Focused Sampling for Low H2S Quantification. Vladislav Achourov and Adriaan Gisolf (Schlumberger), Dave Goodwin and Tim Pritchard (BG Group)

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1 Focused Sampling for Low H2S Quantification Vladislav Achourov and Adriaan Gisolf (Schlumberger), Dave Goodwin and Tim Pritchard (BG Group)

2 Content Challenges, relating to Production of H2S Quantification of H2S Sample Capture Formation Tester Tool Scavenging Mud Scavenging Example Conclusion

3 Challenges: H2S production Safety: H2S is highly toxic safety of personnel during drilling, well testing, and production operations. Corrosion: Appropriate materials required for downhole and surface piping and equipment. Onsite process design: An onsite sweetening plant may be required as part of the production process. Downstream process plant: Sulfur compounds poison catalysts in oil and gas refining and cracking plants The production of byproducts must be managed. Sales gas specifications: Tight controls on sulfur compound concentrations in HC. Environmental and regulatory requirements: Nuisance odors and emission regulations may need to be addressed.

4 Quantification of H2S Scavenging - H2S in formation fluid reacts with filtrate, mud, completion equipment or sampling equipment, resulting in reduced H2S quantities in that fluid Downhole or InSitu H2S Quantification i not possible Fluid Samples analyzed on surface Well testing separator samples Well testing downhole sampling Wireline Formation tester t samples All three methods suffer from Scavenging

5 Sample Capture Methods Well Testing: Extended flow required to Fully remove mud & invaded fluid Fully saturate t completion / surface equipment Difficult to test point of saturation Formation Tester Samples: Need to eliminate i tool scavenging Eliminate filtrate scavenging

6 Scavenging gin Wireline Sampling Operations Minimizing Tool Scavenging Minimize Contact surface area Minimize i i Scavenging per area Minimizing i i i Mud Scavenging requires: Zero bottle fluid contamination No exposure to filtrate in flowline or pump

7 Tool Scavenging, Low Shock Sampling meter 11.5 Quicksilver conventional toolstring 11.5 meter flowline li from probe to lowest sample bottle Large surface area in the pump Potential for (filtrate filled) dead volumes in the pump Exposure to scavenging elastomer seals (~ 30 for standard sampling strings)

8 H2S Scavenging in a regular Low Shock Sampling

9 meter 2.5 Tool Scavenging, g Reverse Low shock Sampling Cleanup Sampling Quicksilver reverse low Shock 2.5 meter probe to bottle No flow through pump Significant ifi reduction in exposure to seals Scavenging parts replaced with Inconel Sample receptacles are coated with SilcoNert 2000

10 Effectiveness of Sulfured coating of the bottles (Reverse Low Shock Sampling)

11 Quicksilver Reverse Low Shock Scavenging g Laboratory Scavenging Testing of Quicksilver & y g g g Q Multi Sampler Tool

12 Mud & Mud Filtrate Scavenging g H2S Scavenging in 450 CC bottle Sulfinert (Siltek /Sulfinert ) coated 450cc sample bottle 5 cc KCL mud filtrate 6000psi and 135 DegC Gas with 40ppm H2S

13 Mud & Mud Filtrate Scavenging g Quicksilver Split flow Ensures minimal i filtrate t captured No exposure to filtrate

14 Example Oil Sampling with Suspected H2S content Challenges: small concentration H2S suspected Well test not deemed economical Sampling environment Depth 3755 MD Max deviation 35 deg 1.85 g/cc OBM 45 bar over balance Mobility < 50 md/cp Potentially movable formation fines

15 Example Toolstring design Quicksilver Reverse low shock Toolstring Low Shock Sample Receptacle, 6 x 450 cc MPSR 1 Gallon Bulk Chamber Compositional i Fluid Analyzer Sample Side Pump, Extra High Pressure Displacement Unit Live Fluid Analyzer Reverse Low Shock Receptacle. 6 x 250 cc coated SPMC Quicksilver Probe Guard Side Pump, High Pressure Displacement Unit

16 Example Filtrate Clean up & Sampling MPSR SPMC SPMC SPMC

17 Example - Results Sample Station completed Under 3 ½ hrs 160 L Pumped Bottles captured with contamination ranging 0 to 2 % weight reservoir fluid 1 to 3 % Stock tank Liquid Sample flashed at surface and analyzed at wellsite Draeger tubes with 3 different sensitivities used No indication of H2S detected

18 H2S From MDT Versus Welltest H2S Concentration From MDT Samples H2S Concentration from Well Test 1 ppm 2 ppm Acknowledgement to Ithaca Energy and ADTI for releasing this example

19 Conclusions With current technology H2S quantification requires sample analysis on surface. Formation Tester Samples need to eliminate tool & filtrate scavenging Minimizing Tool Scavenging Minimize Contact surface area Minimize Scavenging per area Possible utilizing reverse low shock sampling Minimizing Mud Scavenging requires: Zero bottle fluid contamination No exposure to filtrate in flowline or pump Possible utilizing i Quicksilver il