Focused Sampling for Low H2S p gQuantificationVladislav Achourov and Adriaan Gisolf (Schlumberger), Dave Goodwin and Tim Pritchard (BG Group)

Content

Challenges relating toChallenges, relating to Production of H2S Quantification of H2S Quantification of H2S Sample Capture

Formation Tester Tool ScavengingFormation Tester Tool ScavengingMud ScavengingExampleExampleConclusion

Challenges: H2S productiong p

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.

O it d i 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 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.

Quantification of H2SScavenging - H2S in formation fluid reacts with filtrate, mud, completion equipment or sampling equipment resulting in reduced completion equipment or sampling equipment, resulting in reduced H2S quantities in that fluid

D h l I Si H2S Q ifi i ibl Downhole or InSitu H2S Quantification not possible Fluid Samples analyzed on surface Well testing separator samples Well testing downhole sampling Wi li F ti t t l Wireline Formation tester samples

All three methods suffer from Scavenging

Sample Capture Methodsp p

Well Testing: Extended flow required toWell Testing: Extended flow required to Fully remove mud & invaded fluid

F ll t t l ti / f i t Fully saturate completion / surface equipment Difficult to test point of saturation

Formation Tester Samples:N d t li i t t l i Need to eliminate tool scavenging

Eliminate filtrate scavenging

Scavenging in Wireline Sampling Operationsg g p g p

Minimizing Tool ScavengingMinimizing Tool Scavenging Minimize Contact surface area

Mi i i S i Minimize Scavenging per area

Mi i i i M d S i iMinimizing Mud Scavenging requires: Zero bottle fluid contamination No exposure to filtrate in flowline or pump

Tool Scavenging, Low Shock Sampling

Quicksilver “conventional” toolstring11 5 t fl li f b t 11.5 meter flowline from probe to lowest sample bottle

Large surface area in the pump Large surface area in the pump Potential for (filtrate filled) dead

volumes in the pumpmeter

Exposure to scavenging elastomer seals (~ 30 for standard sampling strings)

11.5

strings)

H2S Scavenging in a regular Low Shock SamplingSampling

Tool Scavenging, Reverse Low shock Samplingg g p gQuicksilver reverse low ShockCleanup

2.5 meter probe to bottle No flow through pump

Si ifi t d ti i t Significant reduction in exposure to seals

Scavenging parts replaced with Scavenging parts replaced with Inconel

Sample receptacles are coated mete

r Sampling

with SilcoNert 2000 2.5

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

Quicksilver Reverse Low Shock Scavengingg g

Laboratory Scavenging Testing of Quicksilver & y g g g QMulti Sampler Tool

Mud & Mud Filtrate Scavengingg g

Sulfinert (Siltek®/Sulfinert®) Sulfinert (Siltek®/Sulfinert®) coated 450cc sample bottle

5 cc KCL mud filtrate

H2S Scavenging in 450 CC bottle

6000psi and 135 DegC Gas with 40ppm H2S

Mud & Mud Filtrate Scavengingg gQuicksilver Split flow

E i i l filt t t d Ensures minimal filtrate captured No exposure to filtrate

Example – Oil Sampling with Suspected H2S content

Challenges: small concentration H2S suspected Well test not deemed economical

S li i t Sampling environment Depth 3755 MD Max deviation 35 deg Max deviation 35 deg 1.85 g/cc OBM 45 bar over balance M bilit 50 d/ Mobility < 50 md/cp Potentially movable formation fines

Example – Toolstring designp g gQuicksilver Reverse low shock Toolstring

Low Shock Sample Receptacle, 6 x 450 cc MPSR1 Gallon Bulk ChamberC i i l Fl id A lCompositional Fluid AnalyzerSample Side Pump, Extra High Pressure Displacement UnitLive Fluid Analyzer

Reverse Low Shock Receptacle. 6 x 250 cc coated SPMC

Quicksilver Probe

Guard Side Pump, High Pressure Displacement Unitp, g p

Example – Filtrate Clean up & Samplingp p p g

SPMC

SPMC

SPMC

MPSR

S SS

Example - Resultsp

Sample Station completed Sample Station completed Under 3 ½ hrs 160 L Pumped 160 L Pumped

Bottles captured with contamination ranging 0 to 2 % weight reservoir fluid 0 to 2 % weight reservoir fluid 1 to 3 % Stock tank Liquid

Sample flashed at surface and analyzed at wellsite Sample flashed at surface and analyzed at wellsite Draeger tubes with 3 different sensitivities used No indication of H2S detected No indication of H2S detected

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 exampleexample

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 Minimize Scavenging per area

Possible utilizing reverse low shock sampling

Minimizing Mud Scavenging requires:Minimizing Mud Scavenging requires: Zero bottle fluid contamination No exposure to filtrate in flowline or pump

P ibl tili i Q i k il Possible utilizing Quicksilver