7/27/2019 GEM Water-Based Drilling Fluid Combats Highly Reactive Shales Provides Near Gauge Wellbore

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GEM Water-Based Drilling

Fluid Combats Highly

Reactive Shales, Provides

Near Gauge WellboreLocation: Ship Shoal, Gulf of Mexico

OPERATORS CHALLENGE ANKOR Energy was

looking to switch from an oil-based drilling fluid to a water-based drilling fluid; however, they realized that their typical

choice of gypsum/KCL water-based mud was not going to

provide the inhibition that they needed and that they had

achieved with Baroids ACCOLADE oil-based mud system.

ANKOR Energy wanted to try the water-based system on two

wells in Ship Shoal 229 with measured depths of 8,321 and

7,553. e first well was a build to 20.29 and the second well

was an S-shaped well that built to 52.4 and then dropped back

to vertical by well total depth (TD).

HALLIBURTONS SOLUTION Baroid personnel

conducted an extensive review of shale from the Ship Shoal area.

Below are the x-ray diffraction (XRD) and cation-exchange

capacity (CEC) analyses of shales collected from Ship Shoal 229.

Based on the review, it was determined that the area consisted of

highly reactive shales. Further research showed that offset wells

drilled with various water-based muds had experienced high

dilution rates and washout. Aer additional lab work, Baroid

personnel recommended a custom formulation for the wells

containing Baroids GEM water-based mud system as the base

formulation. Key additives to the formulation included EZ-

MUD shale stabilizer and BARO-TROL PLUS shale stabilizer

to stabilize the wellbore and control filtration rates in the

production section.

ECONOMIC VALUE CREATED Both wells were

successfully drilled without any gumbo attacks. Althoughdilution rates were still high with the GEM system, the wellbore

remained almost gauge in both wells. A 9 7/8 hole was drilled

on both wells, and the average hole size from caliper logs was

10.18 for the first well and 10.22 for the second well. A very

aggressive centralizer program was utilized to run the

production casing on both wells, and the casing on both wells

was successfully run to bottom. e first well utilized a 7 5/8

casing string and the S-shaped well utilized a 7 production

casing. ANKOR Energy was able to drill both wells with a water-

based system and successfully set casing at TD. Had the

operator chosen an oil-based fluid, the costs would have been on

average an added $345,000 per well. e operator believes that

gauge holes enhance the chance of a good cement job for

production strings. Based on the cement bond logs run during

completion operations, the operator classifies the cement jobs on

both wells as very good.

Case History

Fluids Engineering

Baroid

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between Halliburton and the customer that is applicable to the sale. H07616 4/10

6504 ft (1-4-2010) 7485 ft (1-6-2010)

Barite, wt % 8 15

Quartz, wt % 27 24

Plagioclase Feldspar, wt % tr tr

Calcite, wt % 2 2

Dolomite, wt % tr tr

Clay, wt % (smectite, illite, kaolin and chlorite)* 63 59

CEC, meq/100g 22 21