Gas Well Deliquification Workshop Sheraton Hotel, February 17 20, 2013 Foam Injection Via Capillary String in Vicksburg Dry Gas Wells in South Texas Adam Pittman, Brent Jackson, Andrea Jimenez, Dave Senneway Shell South Texas Production Operations
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 2 Outline Background South Texas History South Texas Foam Capillary String Process Example Wells Key Learnings and Conclusions
Production Foamer Background What Does Foam Do For Us? Decrease Surface Tension Lowers Fluid Density Lowers critical gas flow rate - lift liquids at lower flow rate Onset of liquid loading Intermittent production Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop Time 3
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 4 South Texas Vicksburg Background South Texas Asset First wells drilled in 1950 s Asset divested in 2011 550 Producing wells 150 with Foam Injection Corpus Christi Vicksburg Frio Houston SOUTH TEXAS Gulf of Mexico
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 5 Subsurface Background Vicksburg and Frio were primary reservoirs Tight sandstones (0.1-50 md perm) Dry Wet gas (0-30 bbl/mmcf condensate) Reservoirs also contained water (up to 250 bbl/mmcf depending on the well) Typically 30-50 bbl/mmcf Salinity ranged from 8000 ppm chlorides to 90,000 ppm or greater Very little H2S or CO2 No requirement for SCSSV s
Typical Tubingless Well Design With Capillary String Installed Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 6 2-7/8 or 3-1/2 casing with no tubing Stacked pay w/ multiple fractured sands Capstrings installed midperf after well began to liquid load.
Capillary String Selection Process Batch treat well -Compare to SI of similar length at most 6mo earlier, if none available then SI well without batching (same SI time) for comparison Poor No cap string. N WLR > 0.4? F Batch Treat Response N -Examine WB issues (fill / fish / damage) N Y P Y CANDIDATE Condensate <5 bbl/mmcf Y Critical Rate Check AFE/PM Capillary String Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 7
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 8 Production with Foam Injection Foam injection could be widely deployed in different flow conditions and different points in well life. Delaying move into compression Regain production after falling off trend Return slugging wells to constant flow Eliminate intermittent cycles Restore liquid loaded wells
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 9 Foam Example #1 Fell Off Production Trend Down to 200 mcfd prior to Foam Over 1000 mcfd w/ Foam
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 10 Foam Example #2 Intermittent 665 mcfd, 3 bcpd Increased to 1012 mcfd, 12 bcpd
Foam Example #3 Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 11 Liquid Loaded 125 mcfd, 1 bcpd Increased to 350 mcfd, 10 bcpd Liquid Loaded 150 mcfd, 1 bcpd, 0 bwpd average Increased to 350 mcfd, 10 bcpd, 10 bwpd average after CS installation
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 12 Cap String Success Through Time 2007-2010 Program 2007 New selection process introduced 2008 AFE process streamlined 2010 Candidate list exhausted
South Texas Vicksburg Foam Injection Learnings Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 13 Analytical Tools and Trials combined for best prediction of success Turner/Coleman Critical Rate used as a key indicator Batch Treatments also used a key indicator Foam injection via capstring widely deployed Success with Water to Gas ratio as high as 350 bbl/mm Wells with Water to Condensate ratio as low as 50% can still be successfully foamed. Mid Perf placement of capstring better than above top perf placement Depends on fluid level in well Well integrity / casing collapse could prevent optimal capstring placement
Analysis Critical Rate Turner Critical Rate equation with adjustment multiplier (red line) Applied additional correction factor to predict psuedo critical rate with foam (blue line) Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 14
Analysis Critical Rate Critical Rate is the Best Indicator for Success Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 15
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 16 Batch Treatment Screening Uniform Process Compare batch treatment with production following a similar shut-in time.
Batch Treatments in 2009 and Capstring Success Response > 100 mcfd Response ~ 50-100 mcfd Response < 50 mcfd Batch Treatments good indicator for success but even a well with a poor response can respond to continuous foam Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 17
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 18 Analysis Capstring More Effective Mid-Perforation 2008-09 Experiment Mid perf placement shows better response than other placements
Feb. 17 20, 2013 2013 Gas Well Deliquification Workshop 19 Conclusions Well design and environment allowed for continuous foam injection via capstrings at low upfront cost. Foam program in South Texas was very profitable but increased chemical spending significantly as more wells were lifted with foam. Foam injection via capstring could be deployed by trial and error but some analysis and batch treatment tests could be used to more accurately predict continuous foam injection success. Some liquid loaded wells flowing at optimal production rates and responding positively to a batch treatment could still have poor production response to permanent capillary string installation.
DEFINITIONS AND CAUTIONARY NOTE Reserves: Our use of the term reserves in this presentation means SEC proved oil and gas reserves. Resources: Our use of the term resources in this presentation includes quantities of oil and gas not yet classified as SEC proved oil and gas reserves. Resources are consistent with the Society of Petroleum Engineers 2P and 2C definitions. Organic: Our use of the term Organic includes SEC proved oil and gas reserves excluding changes resulting from acquisitions, divestments and year-average pricing impact. The companies in which Royal Dutch Shell plc directly and indirectly owns investments are separate entities. In this announcement "Shell", "Shell Group" and "Royal Dutch Shell" are sometimes used for convenience where references are made to Royal Dutch Shell plc and its subsidiaries in general. Likewise, the words "we", "us" and "our" are also used to refer to subsidiaries in general or to those who work for them. 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