How to Select the Most Reliable Pump for an Application

By Allan R. Budris, P.E.

The writer's past WaterWorld columns have covered individual hydraulic actions that can improve pump mean time between failures (MTBF). This column takes these actions a step further by showing how they can be combined to maximize overall pump reliability. The specific centrifugal pump hydraulic reliability factors covered are Pump Speed, Percent Best Efficiency Flow Rate, Net Positive Suction Head (NPSH) Margin, Suction Energy, and Impeller Material.

It is understood that many of these pump reliability improvement actions could be at the expense of increased initial cost. So the final purchase decision should look at how these reliability improvements will impact the total pump "Life Cycle Costs" (December 2009 Column), since the reduced cost of maintenance and down time, and possible improvements in pump efficiency could far exceed any increase in the initial pump cost. Who knows, if the MTBF is high enough, users could reduce the total initial cost by eliminating the requirement for a back up pump, as some "Best of Class" European pump users do.

PUMP SPEED

Pump manufacturers design their pumps to operate at various speeds, with the maximum (limiting) speed typically based on bearing life, shaft stress, shaft deflection, casing strength, and/or NPSHR. By operating a pump at a slower then maximum speed, the user can see big improvements in bearing and mechanical seal life, plus reductions in cavitation and/or suction recirculation damage (through reduced NPSHR and Suction Energy). Figure 1 plots pump reliability vs. the ratio of the actual-to-maximum allowable pump speed, for two cases (actual field pump failures and laboratory pressure pulsation levels). So, by operating a pump at half its maximum rated speed (say 1,760 rpm vs. a maximum of 3,550 rpm) the relative reliability would be increased from .40 at the maximum speed to .78 at the reduced speed, or approximately twice the MTBF. This reduced speed to 1,760 rpm would also slightly increase the motor efficiency. This increased reliability from lower speeds should also be taken into account when looking to justify a variable speed drive.

PERCENT BEP FLOW RATE

Where a pump operates on its "Head-Capacity" curve and how close the pump is to its best efficiency flow rate is both a pump selection and system issue, since a pump will always operate at the intersection between the pump H-Q and the system H-Q curves. Where the pump operates relative to the pump best efficiency flow rate has a large impact on pump reliability. Although, according to the field data, the best reliability is actually closer to 90%, then 100% of bep.

The reasons for the lower MTBF values at off bep flow rates are increasing pressure force variations around the impeller (higher radial bearing loads) at lower and higher flow rates; suction recirculation at lower flow rates, and more cavitation (higher NPSHR vs. lower NPSHA values) at higher flow rates. All of this can result in lower bearing, mechanical seal, wearing ring, and impeller life.

Typical reasons for pumps not operating near their bep flow rates are

• Including too much head and flow safety margin when selecting a pump.
• The actual system pressure drop is different than the initial calculated value.
• The system flow demand is different than the initial assumption.
• Changes to the system over time.
• Corrosion and wear of the pump and/or system.

Actual field testing (see Jan 2009 Column) is the best way to determine the true current system H-Q curve, which shows where the pump is actually operating relative to the pump bep flow rate. Once the actual system H-Q curve has been established, hardware changes to better match the pump and system can then be made, such as a new pump, new pump impeller (or impeller trim), or changes in the pump control method, such as the addition of a Variable Speed Drive.

NPSH MARGIN

As discussed in last month's column, the amount of NPSH Margin provided to a pump, above the NPSHR (especially with High Suction Energy Pumps and/or pumps operating in the Suction Recirculation Region), can have a large impact on the reliability of the pump, as shown in figure 2. Typically you need a NPSH margin ratio of at least 4.0 (NPSHA/NPSHR), in the allowable operating range (above the start of suction recirculation), to eliminate all cavitation in a pump. This is why the maximum reliability, shown in figure 2, peaks at a NPSH margin of 4.0.

Figure 3 also shows this "NPSH Margin-Reliability" relationship, but for High Suction Energy pumps, where the suction pressure pulsations (which can have a direct impact on pump life) actually peak at NPSH Margin ratios in the range of 1.4 to 2.3 (depending on whether or not the pump is in suction recirculation). The reduction in pressure pulsations at NPSH Margin ratios below this peak value is caused by the increasing amounts of dissolved air that come out of solution at lower pressures (see June 2009 column).

SUCTION ENERGY

Based on many years of experience, and actual field data, it has been found that the higher the pump Suction Energy, the lower the pump reliability, above a value of about 70 x 106. Suction Energy is the product of the pump speed (in RPM); impeller eye diameter (in inches); Suction Specific Speed (which is impacted by the impeller eye diameter); and the liquid specific gravity. But it is the pump type that determines the specific Suction Energy levels where vibration (High Suction Energy) and cavitation damage (Very High Suction Energy) starts in a pump (as shown in Table 1). As can be seen, the most sensitive pump type to elevated suction energy levels are pumps with little or no impeller vane overlap, such as two vaned impellers, while inducer pumps have the highest gating values.

SUCTION ENERGY/NPSH MARGIN COMBILED RELIABILITY

As mentioned above, there is a correlation between the Suction Energy of a pump and the NPSH Margin. Higher Suction Energy requires more NPSH Margin to suppress cavitation damage. The writer has combined these two factors into two reliability plots, comparing the ratio of the "Suction Energy Ratio" (pump Suction Energy divided by the High Suction Energy gating value for the pump type), with the "NPSH Margin Ratio" (NPSHA/NPSHR). Figure 4 is based on actual field MTBF reliability values, while figure 5 is based on Suction Pressure Pulsation levels.

IMPACT OF DIFFERENT IMPELLER MATERIALS ON PUMP LIFE

The final factor that can have a very large impact on the impeller cavitation damage component of pump life (experienced by High and Very High Suction energy pumps) is the material that the impeller is made of, as shown in Table 2. So changing from mild steel (reliability factor of 1.0) to stainless steel (reliability factor of 4.0), would increase the impeller life from cavitation damage by a factor of 4. Hard coatings, such as ceramic, can also increase impeller life.

COMBINING HYDRAULIC PUMP LIFE FACTORS

The net impact of all of the above individual reliability factors can be determined by combining their product to yield the "total relative reliability". This can be especially useful when comparing pump options for a specific application. Table 3 shows how the writer combined these hydraulic life factors for a problem pump installation at a major pump user. Four options were evaluated, with the relative reliability ranging from .29 for the current problem pump (which experienced a MTBF of about six months), to 2.00 for the best option (with a VFD). This means that the current six month life would be expected to increase to around 4 years, by selecting option #4.

CONCLUSIONS

So as spelled out above, this column provides the reliability conscious pump user with tools that can help select the most reliable pump for an application, and reduce overall life cycle pump costs.

About the Author: Allan R. Budris, P.E., is an independent consulting engineer who specializes in training, failure analysis, troubleshooting, reliability, efficiency audits and litigation support on pumps and pumping systems. With offices in Washington, NJ, he can be contacted via e-mail at budrisconsulting@comcast.net.

February Offshore Magazine

 

The February 2012 issue of Offshore is available to view or download. Click here to View in your Browser! Click here to Download Qmags PDF Follow us on Facebook Follow us on Twitter Dear Subscriber, This note is your reminder that this month's issue of Offshore is available to view or download. Feature Articles Drilling contractors ready fleet for upcoming activity Asia/Pacific struggles to meet regional demand Outlook for Australian offshore remains bright Rockhopper advances Falkland Islands prospects Innovation of tools, service key to successful well abandonment Shell grapples with uncertainties of Brent field decommissioning Marginal deepwater developments: Innovative engineering approach makes it possible Subsea innovations make complex Islay tieback possible Subsea Tieback Forum & Exhibition opens March 6 Meters, sampling critical for effective multiphase flow management Departments Online Vessels, Rigs, & Surface Systems Comment Drilling & Production Data Geosciences Global E&P Offshore Automation Solutions Offshore Europe Business Briefs Gulf of Mexico Advertisers' Index Subsea Systems Beyond the Horizon Other resources available from PennWell Offshore Maps & Posters PennEnergy.com Research and Data PennWell Books Fall 2011 Energy Catalog For DOWNLOAD INSTRUCTIONS: http://www.qmags.com/DownloadingHelp.asp To reach our HELP DESK, please visit: http://www.qMags.com/help To view the archived files on your Qmags account, please click here. .

A Good Year for O&G Industry

The outlook of the world's oil and gas industry is expected to remain buoyant this year, said Acteon Group analyst Will Rowley.

"Its (2012) going to be a good year. If you look at financial results of major operators and contractors, 2011 was better than 2010.

"So, there is no reason this year should not be any better than 2011. There is no shortage of works, only margin to improve and a little bit of cost," said on the sidelines of the three-day Offshore Asia conference and exhibition 2012 here yesterday.

For instance, he cited in the last few days, Schlumberger and Halliburton announced more than 40 per cent increase in their profitability year-on-year.

"There was also increased profitability across major listed companies and operators, and in terms of cash in hand, it has gone up."

In his presentation, Rowley said offshore oil is on an upward trend again. "All activities are increasing, supported by cash-rich operators. There are opportunities in new frontier areas through innovation of products, services and working method.

"Exploration is increasing but geographically diverse. Deepwater continues to dominate short-term expenditure and the floating liquefied natural gas/liquefied natural gas is fast becoming a growing niche market."

Moving forward, Rowley said the industry's capital expenditure is expected be close to a record level of about US$500 billion (RM1.52 trillion) this year.

"There are also technical challenges that would cause more money to be spent," he added.

He cited that listed exploration and production companies have in excess of US$200 billion (RM606 billion) in cash, while listed oilfield services firms have in excess of US$48 billion (RM145.44 billion) of cash.

On the local front, Rowley said Malaysia is an exciting country for companies like Acteon to work in as there is a lot of potentials in the domestic oil and gas sector.

Meanwhile, Petronas development and production senior general manager for petroleum engineering Chen Kah Seong said the national oil company is intensifying its domestic exploration as well as looking at high-value assets overseas as part of its strategies to sustain oil and gas reserves.

He said information pertaining to Malaysia's oil and gas reserves life span can be obtained when Petronas announced its financial year results next month.

Copyright 2012 New Straits Times Press (Malaysia) Berhad All Rights Reserved

Customer Satisfaction with Hydraulic Fracturing Services Diminishes

U.S. demand for hydraulic fracturing services continues to rise along with shale exploration, but customers indicate they are less satisfied with these services in comparison to other completion-related services they receive, according to a recent survey by EnergyPoint Research.

The potency and cleanliness of hydraulic fracturing capabilities continues to increase thanks to technological advances, and nominal hydraulic fracturing capacity looks on pace to grow by 25 percent or more in 2012.

However, the current environmental and political climate has prompted suppliers to invest heavily in both new fracturing technology and equipment, adding to costs at a time when customers are already nervous about low natural gas prices.

The ramification has been that in the high frac-intensive North American land market, the industry's "Big Three" – Halliburton, Schlumberger and Baker Hughes – have seen their customer satisfaction ratings fall to materially low levels over the last 24 months, EnergyPoint reported.

Market leaders in the frac space are working hard to differentiate their services in the minds of customers, EnergyPoint noted.

"Centralization of crews and resources, packaging of proppant technologies, use of proprietary materials to redirect hydrocarbons around proppants, and deeper blasts into rock formations are all part of today's next-generation approach to the high-profile service.," EnergyPoint added.

However, domestic customers still seem relatively disenchanted with suppliers' performance despite all the "super fracking."

Halliburton, the largest U.S. market shareholder, will hold 2012 capacity additions steady with 2011 levels, while Schlumberger and Baker Hughes seek to step up domestic capacity and extend their footprints internationally. The shortage of frac capacity has also encouraged some integrated providers to require bundled purchases from customers in exchange for the right to access their in-demand frac crews.

"Alas, the previous EnergyPoint analyses suggest this only serves to rankle customers further," EnergyPoint commented.

Limited customer evaluations gathered by EnergyPoint indicated that second-tier service players such as FTS International, Trican and Weatherford International could have an opportunity to move deeper into unconventional shales, given the capacity shortage for hydraulic fracturing services.

Karen Boman has more than 10 years of experience covering the upstream oil and gas sector. Email Karen at kboman@rigzone.com.

Community College Offers Fast-Track for O&G Careers

The surge in the oil and gas industry activity has created demand for a wide array of jobs, ranging from professionals such as geologists and engineers to skilled blue-collar jobs, including technicians, welders and electricians.

To meet the surge in local demand for skilled technical workers, Houston-based community college system Lone Star College has expanded its curriculum to include the oil and gas industry.

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Last year, the college established its Energy and Manufacturing Institute to offer training for jobs in the oil and gas industry. Through this institute, students are taught a combination of skills to prepare them for careers in petroleum field services and automated manufacturing.

The institute offers two pre-apprenticeship certification programs that last six weeks – an engineering technician program and machining program. A machinist fabricates all the parts that go on a rig or subsea valve, while the engineering technicians put everything together and keep things running.

Lone Star last year offered 60 slots through a state-funded grant for its engineering technician assistant pre-apprenticeship program. Due to an overwhelming demand, all slots for the grant program have been filled at this point. While the machining program does have a tuition cost, students can apply for financial aid through their local Workforce Solutions Center.

Through these newest set of programs, students can be trained to work on a land or subsea rig or in a manufacturing assembling company.

Students who participate in these programs can do an internship or pre-apprenticeship with an oil and gas company as they are participating in these programs, or after they complete the program, to gain on-the-job training. Once they complete the pre-apprenticeship programs, they can either move into a more in-depth program at Lone Star College System or transition into the workforce.

"We're trying to help companies find workers with fast entry-level type programs to meet demand," said David Lenzi, director of energy & manufacturing for Lone Star College System.

Lenzi sees the college's programs as a way to fill demand for skilled blue collar jobs, such as machinists, as the number of oil service and manufacturing companies open facilities, particularly in the I-10, Highway 249 and Beltway 8 area. According to Lone Star, a 14 percent increase in engineering technology careers will take place in Texas between 2008 and 2018.

The college has been in discussions with companies considering a move to the city, informing them of the educational opportunities that exist here. Lone Star officials also have been seeking to further relationships with oil and gas companies to partner with the college on training opportunities, such as a simulation rig on which students can train in a real-world setting. The location of this simulation rig has not yet been determined.

Beyond these two fast-track programs, students can go on to earn other certifications for energy-related careers, including engineering technician, machine shop assistant, machine tool operator and welders, associate's degrees and bachelor degrees through Lone Star's university partners, which include the University of Houston and Sam Houston State University.

Starting March 1, the college in partnership with PetroEd will offer a pre-certification training program for oil and gas that's geared towards accountants, sales managers and technical/business professionals who are new to the energy industry, investors and financial professionals seeking to understand oil and gas and all levels of petroleum industry support staff.

This course will teach the basics of upstream and downstream oil and gas, from how oil deposits are formed to how oil and gas are converted into products for the downstream energy industry.

Lone Star also offers customized corporate training and professional development seminars for current oil and gas workers.

Last month, the college opened a new facility, Lone Star College-University Park, at the Hewlett-Packard campus off Highway 249. The new facility, which includes 1.6 million square feet of space acquired from HP, consists of several buildings where oil and gas related training is held.

Lone Star is inviting oil and gas related companies to rent space in the building and share the lab. One oil and gas company is at the site already, and has dedicated space on an entire floor of one of the buildings at the new facility.

Officials are also seeing a diverse array of students enrolling in its oil and gas programs, from recent high school graduates to veterans to unemployed and underemployed mid-career workers seeking transition to a new career.

Lone Star College is seeking corporate partners to add support to its oil and gas training programs and instructors for its credit and non-credit course and corporate training programs geared towards oil and gas. The college is in need of instructors with engineering, geology and technical backgrounds, such as welding and machining, to fill several positions available.

"We're looking for retirees from the oil and gas industry, people with experience who want to help give back to the next generation," said Lenzi, noting that it's difficult to hire individuals still working in oil and gas due to the higher salaries.

21st Century Trends for Apprenticeships

Additionally, the school has been working with other technical and community colleges around the country to expand apprenticeship opportunities for students. Lone Star, along with Midlands Technical College in Columbia, S.C., Three Rivers Community College in Norwich, Conn.; and Polk State College in Winter Haven, Fla., co-authored a white paper on the benefits of apprenticeships in the U.S., 21st Century Apprenticeship Models: A National Council for Continuing Education and Training.

While apprenticeships typically were handled through traditional academic departments, apprenticeships today are originating from community colleges, continuing education programs and corporate training departments.

"Rapid changes in our industrial system require a large body of skilled workers who are able to carry out technical specifications and who can supervise less skilled members of the workforce," officials from the school noted in the paper.

Apprenticeship programs such as the programs offered at Lone Star can provide workers seeing to transition to new careers, who are unemployed or left school early.

"At a time when America is experiencing a shortage of skilled workers, apprenticeships provide a structured approach to fill the high tech, middle-skill jobs required to boost the nation's economy," according to Linda Head, associate vice chancellor for workforce development at Lone Star.

However, a number of issues must be addressed to promote more training through apprenticeships in the U.S. The long shifts that employees typically work can interfere with time needed to accomplish theory work, making online courses and hybrid courses of theory and hands-on work more important than before.

The fact that employees are coming into the workforce with fewer technical skills – and that apprenticeships today are two years or less versus longer apprenticeships in the past – also must be taken into consideration, Head noted.

Karen Boman has more than 10 years of experience covering the upstream oil and gas sector. Email Karen at kboman@rigzone.com.

Iraq Crude Oil Export Expansion Project Phase 1

The Iraq Crude Oil Export Expansion Project (ICOEEP) is perhaps the most important strategic project in the Iraqi Ministry of Oil's (MoO) Master Plan. The Crude Export Facility of Southern Iraq currently exports approximately 1.8 MMBOPD from onshore facilities to the KAAOT and ABOT offshore terminals.

The MoO Master Plan 2007 has the objective of developing further offshore loading facilities to enable export capability of 4.5 MMBOPD within 5 years. The ICOEEP Project is designed to achieve this objective.

ICOEEP Phase 1 includes the following scope of works on a full engineering, procurement, construction and commissioning basis:

• Installation and commissioning of two 48" parallel pipelines, 20km onshore and 120km offshore.
• Installation of three SPM systems (single point mooring systems) capable of receiving and loading VLCC tankers.
• Fabrication and installation of a 600MT Subsea Valve Manifold.
• Dredging works to achieve pipeline trenching and sufficient water depth for VLCC mooring.
• Construction and commissioning (civil, mechanical and electrical works) for the new onshore facilities at Fao terminal.
• Installation of subsea Fibre Optic Cables and Composite Power Fibre Optic Cables.
• Installation and commissioning of Telecommunications and SCADA systems.
• Full commissioning, Client training and initial operation responsibilities to ensure the Client is equipped to operate and maintain the new exporting facilities.

In order to achieve the Client's fast-track schedule Leighton will engage three of its latest offshore construction and pipe lay vessels; the Leighton Eclipse, Leighton Stealth, Leighton Mynx, as well as a fleet of support and security management vessels.

http://www.ziddu.com/download/18595788/Iraq_Crude_Oil_Export_Expansion_Project_Phase_1.pdf.html

Iraq opens offshore oil facility

Bloomberg

Published: 00:00 February 13, 2012

Baghdad:  Iraq, seeking to maximise crude oil exports, opened the first of four planned offshore mooring facilities in the Arabian Gulf and intends by March to add 200,000 barrels a day to its capacity for loading tankers there.

The new single-point mooring unit, extending into the sea from the southern oil terminal of Fao, has a potential export capacity of 850,000 barrels a day, Falah Al Ameri, chairman of the State Oil Marketing Organisation, said in an interview.

Hussain Al Shahristani, deputy prime minister for energy affairs, said in a separate interview yesterday that Iran probably won't shut the Strait of Hormuz. "This would affect all the countries, including Iran itself," he said of that nation's threats to close Hormuz in response to sanctions over its nuclear programme. "We are working with other countries to contain the situation and make sure crude exports in the region are not affected."

Iraq holds the world's fifth-largest crude deposits, including Canadian oil sands, according to data from BP Plc. The government is trying to attract foreign investment and expertise to help boost energy exports and rebuild an economy shattered by years of conflict, sanctions and sabotage.

The four offshore units would increase the country's export capacity by a combined 3.4 million barrels a day by 2013. Iraq, with a narrow coastline pinched between Kuwait and Iran, plans to install an undersea pipeline to each unit and load oil aboard tankers capable of mooring there. The nation also exports crude overland by pipeline through neighbouring Turkey.

"We are ready to market these new capacities, particularly in promising markets in Asia where our crude exports to China currently average 500,000 barrels a day," Al Ameri said during a ceremony that Prime Minister Nouri Al Maliki attended to inaugurate the facility.

Leak Off Test (Procedures and Calcuation)

Leak Off Test is conducted in order to find the fracture gradient of certain formation. The results of the leak off test also dictate the maximum equivalent mud weight that should be applied to the well during drilling operations.

Leak Off Test (LOT) guide line procedures are as follows (note: this is just only guide line. You may need to follow your standard procedure in order to perform leak off test):

1.Drill out new formation few feet, circulate bottom up and collect sample to confirm that new formation is drilled to and then pull string into the casing.

2.Close annular preventer or pipe rams, line up a pump, normally a cement pump, and circulate through an open choke line to ensure that surface line is fully filled with drilling fluid.

3.Stop the pump and close a choke valve.

4.Gradually pump small amount of drilling fluid into well with constant pump stroke. Record total pump strokes, drill pipe pressure and casing pressure. Drill pipe pressure and casing pressure will increase continually while pumping mud in hole. When plot a graph between strokes pumped and pressure, if formation is not broken, a graph will demonstrate straight line relationship. When pressure exceeds formation strength, formation will be broken and let drilling fluid permeate into formation, therefore a trend of drill pipe/casing pressure will deviate from straight line that mean formation is broken and is injected by drilling fluid. We may call pressure when deviated from straight line as leak off test pressure.

Note: the way people call leak off test pressure depends on each company standard practices.

Leak off test pressure can be calculated into equivalent mud weight in ppg as formula below:

Leak off test in equivalent mud weight (ppg) = (Leak off test pressure in psi) ÷ 0.052 ÷ (Casing Shoe TVD in ft) + (current mud weight in ppg)

Pressure gradient in psi/ft = (Leak off test pressure in psi) ÷ (Casing Shoe TVD in ft)

Example:

Leak off test pressure = 1600 psi
Casing shoe TVD = 4000 ft
Mud weight = 9.2 ppg

Leak off test in equivalent mud weight (ppg) = 1600 psi ÷ 0.052 ÷ 4000 ft + 9.2ppg ppg = 16.9

Pressure gradient = 1600 ÷ 4000 = 0.4 psi/ft

4.Bleed off pressure and open up the well. Then proceed drilling operation.

Please find the Excel sheet to calculate leak off test

Formation Integrity Test (FIT) Procedure and Calcualtion

Formation Integrity Test is the method to test strength of formation and shoe by increasing Bottom Hole Pressure (BHP) to designed pressure. FIT is normally conducted to ensure that formation below show will not be broken while drilling the next section with higher BHP. Normally, engineers in town will design how much formation integrity test pressure required mostly in ppg.

Before forming formation integrity test, you should know pressure required for Formation Integrity Test. The formula showed below demonstrates you how to calculate required FIT pressure.

Pressure required for FIT (psi) = (Required FIT in ppg – Current Mud Weight in ppg) x 0.052 x True Vertical Depth of shoe in ft

Example:
Required FIT (ppg) = 14.5
Current mud weight (ppg) = 9.2
Shoe depth TVD (ft) = 4000 TVD
Pressure required for FIT = (14.5-9.2) x 0.052 x 4000 = 1102 psi

Formation Integrity Test (FIT) guideline is listed below: (note: this is just only guide line. You may need to follow your standard procedure in order to perform formation integrity test):

1. Drill out new formation few feet, circulate bottom up and collect sample to confirm that new formation is drilled to and then pull string into the casing.

2. Close annular preventer or pipe rams, line up a pump, normally a cement pump, and circulate through an open choke line to ensure that surface line is fully filled with drilling fluid.

3.Stop the pump and close a choke valve.

4. Gradually pump small amount of drilling fluid into well with constant pump stroke. Record total pump strokes, drill pipe pressure and casing pressure. Pump until casing pressure reaches the pressure required for formatin integrity test. Hold pressure for few minutes to confirm pressure.

5. Bleed off pressure and open up the well. Then proceed drilling operation.

Please find the Excel sheet to calculate pressure required for formation integrity test.

Seabed oil test off Angola beats driller's expectations

Cobalt International Energy Inc. said results from tests at a deep sea oil well off Angola had exceeded expectations and had increased the company's confidence in its West African pre-salt exploration prospects.

Analysts and investors believe drilling thousands of metres under the Kwanza Basin seabed through blocks known as pre-salt could match huge discoveries made off the Brazilian coast in similar rock formations.

Cobalt, whose main stakeholder is Goldman Sachs, said tests at its Cameia-1 well in Block 21 confirmed the presence of a 360-metre "gross continuous oil column."

Analysts at Citi said the test results were "quite impressive" and the well's reserve potential could exceed two billion barrels and be worth up to $2.6 billion.

© Copyright (c) The Edmonton Journal

Pump Output Calculation for Duplex Pump and Triplex Pump

Rig pump output, normally in bbl per stroke, of mud pumps on the rig is important figures that we really need to know because we will use pump out put figures to calculates many things such as bottom up strokes, wash out depth, tracking drilling fluid, etc. In this post, you will learn how to calculate pump out put for triplex pump and duplex pump.

Triplex Pump Output Formula

Triplex Pump Output in bbl/stk = 0.000243 x (liner diameter in inch) ² X (stroke length in inch)

Example: Determine the pump output in bbl/stk at 100% and 97% efficiency
Linner size = 6 inch
Stroke length = 12 inch
Triplex pump output:
PO @ 100% = 0.000243 x 6² x 12
PO @ 100% = 0.104976 bbl/stk

Adjust the triplex pump output for 97% efficiency:
Decimal equivalent = 97 ÷ 100 = 0.97
PO @ 97% = 0.104976 bbl/stk x 0.97
PO @ 97% = 0.101827 bbl/stk

Duplex Pump Output Formula

Duplex Pump Output in bbl/stk = 0.000162 x S x [2(D)² - d²]

Whrere:
D = liner diameter in inch
S = stroke length in inch
d = rod diameter in inch

Example: Determine the duplex pump output in bbl/stk at 100% and 85% efficiency

Liner diameter = 6 inch
Stroke length = 12 inch
Rod diameter = 2.0 in.

Duplex pump efficiency = 100 %.
PO @ 100% = 0.000162 x 12 x [2 (6) ² -12² ]
PO @ 100% = 0.13219 bbl/stk

Adjust pump output for 85% efficiency:
PO @ 85% = 0.132192 bbl/stk x 0.85
PO @ 85% = 0.11236 bbl/stk

Please find the Excel sheet to calculate triplex pump output and duplex pump output

Annular Velocity (AV) Calculation

Annular Velocity (AV) is how fast of fluid in annulus is traveling. Three main factors affecting annular velocity are size of hole (bigger ID), size of drill pipe (smaller OD) and pump rate. This post will show you how to calculate annular velocity in feet per minute with different formulas.

Formula#1: Annular velocity (AV) in ft/min

Annular velocity in ft/min = Flow rate in bbl/min ÷ annular capacity in bbl/ft

Example:
Flow rate = 10 bbl/min
Annular capacity = 0.13 bbl/ft
AV = 10 bbl/min ÷ 0.13 bbl/ft
AV = 76.92 ft/mim

Formula#2: Annular velocity (AV) in ft/min

Annular velocity in ft/min = (24.5 x Q) ÷ (Dh² – Dp²)

where
Q = flow rate in gpm
Dh = inside diameter of casing or hole size in inch
Dp = outside diameter of pipe, tubing or collars in inch

Example:
Flow rate (Q) = 800 gpm
Hole size = 10 in.
Drill pipe OD = 5 in.
AV = (24.5 x 800) ÷ (10² – 5²)
AV = 261 ft/mim

Formula#3: Annular velocity (AV) in ft/min
Annular Velocity in ft/min = Flow rate (Q) in bbl/min x 1029.4÷ (Dh² – Dp²)

Example:
Flow rate (Q) = 13 bbl/min
Hole size = 10 in.
Drill pipe OD = 5 in.
AV = 13 bbl/min x 1029.4 ÷ (10² – 5²)
AV = 178.43 ft/min

You also can back calculate how much flow rate you want for desired annular velocity in feet per minute as per following formulas.

Flow rate required in gpm = (AV in ft/min) x (Dh² – DP²) ÷ 24.5

AV = desired annular velocity in ft/min
Dh = inside diameter of casing or hole size in inch
Dp = outside diameter of pipe, tubing or collars in inch

Example:
Desired annular velocity = 120 ft/mm
Hole size = 10 in
Drill pipe OD = 5 in.
Flow rate required in gpm = 120 x (10²- 5²) ÷ 24.5
Flow rate required in gpm = 367.4 gpm

Moreover, you can calculate strokes per minute (SPM) required for a given annular velocity in feet per minute as well. The idea is to use the formula above and devided by pump output in bbl/stk. Let's review the fomula.

SPM = (AV in ft/min x annular capacity in bbl/ft) ÷ pump output in bbl/stk

AV = desired annular velocity in ft/min

Example
Desired annular velocity in ft/min = 120 ft/min
Dh = 12-1/4 in.
Dp = 4-1/2 in.
Annular capacity = 0.1261 bbl/ft
Pump output = 0.136 bbl/stk
SPM = (120 ft/mm x 0.1261 bbl/ft) ÷ 0.136 bbl/stk
SPM = 111.3 spm

Please find the Excel sheet for calculating annular velocity

Petrobras struggles with equipment shortfalls

Petrobras cut investment in 2011 for the first time in eight years as Brazil's state-run energy company struggled to buy the equipment, technology and services needed to carry out its $225 billion expansion plan to exploit one of the world's most promising offshore oil frontiers, a report said.

Petrobras invested 72.5 billion reais ($42.05 billion), a 5.1% drop from 76.4 billion reais in 2010, company executives said on Friday according to Reuters.

A day earlier, Petrobras said fourth-quarter profits tumbled 52% on sluggish oil output and refineries so overtaxed that the country has had to boost gasoline imports.

Petrobras shares tumbled on Friday, headed for their biggest daily decline since August due to falling profit, sluggish production growth and news of an expensive equipment order for offshore rigs.

Incoming chief executive Maria das Graças Foster must improve this performance if Petrobras is to achieve its goal of nearly tripling output to 6.4 million barrels a day in 2020, enabling Brazil to challenge the United States as the world's No. 3 oil producer.

"The challenges we face are structural," said José Sérgio Gabrielli, who will step down on Monday after more than six years as chief executive. "We are definitely in a moment of transition."

That transition involves turning $150 billion of active but unfinished investments into operating projects, said Almir Barbassa, chief financial officer.

Those projects have been held up by world-wide shortages of everything from giant steel spheres for refineries to jet turbines to power oil platforms, said Renato Duque, Petrobras' head of supply services.

"It's not just in Brazil, it's international," he said at a news conference at company headquarters in Rio de Janeiro. "There are shortages of everything."

Those shortages, though, may soon get worse.

On Thursday Petrobras told Reuters it agreed to pay a whopping $76.3 billion over 15 years to lease 26 deepwater oil drilling rigs from Brazilian company Sete Brasil and Cyprus's Ocean Rig.

Petrobras shares slid more than 6% on Friday due to the sharp decline in profit and the new rig order, which included five more drill ships than first planned. Petrobras preferred shares fell 6.82% to 23.76 reais in Sao Paulo, wiping nearly a third off this year's gains.

On Thursday, the company reported fourth-quarter net income of 5.05 billion reais, down sharply from 10.60 billion reais in the same quarter of 2010 and far below the 9.20 billion real average estimate of 10 analysts surveyed by Reuters. It was also lower than Petrobras' third-quarter profit of 6.33 billion reais.

Petrobras' difficulties in meeting targets or keeping up with demand extend to most of its major operational units.

Its profits were crimped in 2011 by surging demand for gasoline. Soaring vehicle sales and transport in Brazil are straining the company's domestic refining capacity and led to the import of 70,000 barrels a day of gasoline in December, a record high.

Gabrielli said the growth in Brazil's fuel market simply exceeded Petrobras' ability to keep up.

"It's impossible to foresee in normal circumstances that the consumption of fuels would grow at three times the rate of (gross domestic product)," Gabrielli said.

He said a ramp-up in the company's production of gasoline, cooking gas, diesel and naphtha had reached a limit. Fuel supply problems, he added, would not be resolved until 2013.

The problems, he said, were caused by a drop in ethanol production.

Because biofuels complement Brazil's overall fuel market, any shortfall in its ethanol supply causes a spike in demand for gasoline and other fossil fuels.

"The problem isn't in the oil industry, but in the ethanol sector," said Gabrielli. Ethanol output fell due to a poor cane harvest last year. The crop yield is expected to improve in 2012.

Brazil's huge cane ethanol industry produces the biofuel for an auto fleet where more than 90 percent of all new cars sold are flex-fuel vehicles, which can run on any mix of ethanol and gasoline.

Drivers tend to switch between ethanol and gasoline when supply and demand factors make one or the other better value for money.

Despite huge investments, Petrobras's global output of 2.72 million barrels a day was lower in December than a year earlier.

Barbassa, the CFO, said domestic oil output could have been 40,000 barrels per day higher were it not for unplanned platform outages. The company produces just over 2 million barrels of oil a day in Brazil.

Net debt rose to 54.9 billion reais, up from 36.6 billion reais in 2010 and that 150 billion reais in active, unfinished investments would boost future results.