Groundwater Protection:Proper Drilling of Surface Hole

and Cementing of Surface Casing

B. Scott HinesPresident/Engineer

GROUNDWATER PROTECTION

• Surface Casing Purpose

• Carrizo Wilcox Aquifer Facts/Map/Log

• Proper Surface Hole Drilling Practices• Drilling Guidelines• Drilling Fluid Guidelines• Casing Running Guidelines• Cement System Guidelines• RRC Guidelines• GAU Recommendation Letter• Rule 13 Concerns• Centralizer Style

Surface Casing Purpose Protect Fresh Water Sands

Maintain Wellbore Stability

Prevent Lost Returns in Shallow Sands

Provide Kick Tolerance While Drilling Production hole

Support BOP Stack and Subsequent Casing Strings

Carrizo Wilcox Aquifer

The Carrizo-Wilcox Aquifer is a major aquifer extending from the Louisiana border to the border of Mexico in a wide band

adjacent to and northwest of the Gulf Coast Aquifer. It consists of the Wilcox Group and the overlying Carrizo Formation of the

Claiborne Group. The aquifer is primarily composed of sand locally inter-bedded with gravel, silt, clay, and lignite. Although the Carrizo-Wilcox Aquifer reaches 3,000 feet in thickness, the freshwater saturated thickness of the sands averages 670 feet.

Carrizo Wilcox Aquifer

The groundwater, although hard, is generally fresh and typically contains less than 500 milligrams per liter of total dissolved solids in the outcrop, whereas softer groundwater with total

dissolved solids of more than 1,000 milligrams per liter occurs in the subsurface. High iron and manganese content

in excess of secondary drinking water standards is characteristic of the deeper subsurface portions of the

aquifer. Parts of the aquifer in the Winter Garden area are slightly to moderately saline, with total dissolved solids

ranging from 1,000 to 7,000 milligrams per liter.

Carrizo Wilcox Aquifer

Irrigation pumping accounts for slightly more than half the water pumped, and pumping for municipal supply accounts for another 40 percent. Water levels have declined in the Winter

Garden area because of irrigation pumping and in the northeastern part of the aquifer because of municipal

pumping.

Eagleford Shale Map

Typical Carrizo Wilcox Aquifer LogTop Of

Carrizo

Aquifer

Bottom

Of

Carrizo

Aquifer

Drilling Guidelines Standard Bit Size

12-1/4”

Standard Casing Size 9-5/8”, 40#, N-80

Run Stabilizers at 30’ & 60’ 1/8” undergauge

Back Ream all Connections

Control Drill Carrizo Section at 100 FPH

Wiper Trip to Rotary after Section TD’d

Minimize Swabbing & Surging once Carrizo Wilcox section has been drilled

Drilling Fluid Guidelines

• Maintain MW 8.8 # to 9.2#

• Plastic Viscosity 4-10 cps

• Yield Point 10-24 cps

• Ph 8.5 to 9.0

• LGS 4%-5%

• Pump Gel sweeps every 500’. Can be achieved by adding PHPA directly into DP every 100”. Will also minimize bit balling.

• Add SAPP to thin mud if funnel viscosity is over 60

• If losses occur in Carrizo Wilcox small additions of LCM will help, wholesale losses in Carrizo Wilcox are difficult to remedy.

Casing Running Guidelines• Run Float Shoe and Float Collar

• Run Turbolizers on Shoe Track (2 jts.)

• One Turbolizer thereafter every 4th jt. Through Wilcox Aquifer

• One Centralizer thereafter every 4th jt. To surface

• Run casing slow to minimize surge effect on formation

• Install circulating iron and circulate out clean 200’ above top interval of Carrizo Aquifer

• Circulate minimum two annulus volumes prior to cementing

Typical Cement System • Lead Slurry: • 15/85 POZ (Fly Ash) & Class “A” Cement + 3% BWOW

Sodium Chloride + 0.4% BWOC R-3 + 0.01 GPS FP-6L + 12% BWOC Bentonite. Density 12.40 ppg, Yield 2.31 cf/sack. Free Water 2.6 mls at 90 degrees angle

• Compressive Strength:

• 12 hrs @ 80 Degrees. 145 #

• 24 hrs @ 80 Degrees. 359 #

• 72 hrs @ 80 Degress. 710 #

Typical Cement System • Tail Slurry:

• Premium Class “A” + 0.3% BWOC R-3 + 0.01 gps FP-6L. Density 15.60 ppg, Yield 1.18 cf/sack. Free Water 1.8 mls @ 90 degrees angle

• Compressive Strength:

• 12 hrs @ 80 Degrees. 1445 #

• 24 hrs @ 80 Degrees. 2240 #

• 72 hrs @ 80 Degress. 3348 #

GAU Recommendation Letter

RRC Rule 13 Basic Guidelines If Casing Set Below 3500’ need approval from RRC

• Method of Well Control• Kill Weight Mud on location• Adequate Barite on location• Diverter system installed

• Cement must be circulated to ground surface. Must Notify RRC if cement is not circulated to ground surface immediately for remedial procedure

• Demonstrate bonding of casing/cement/formation to prevent gas migration. San Miguel Coal Seam has caused problems.

Lead Slurry Compressive strength 250# in 24 hrs. Free Water 6 mls

Tail Slurry (critical cement) Compressive strength 1200# in 72 hrs. Free Water 2 mls

Casing Test Requirements: 0.5 #/ft with maximum of 1500# after NU of BOP’s Subsequent test after 360 rotating hours.

See Texas RRC Section 3 Rules Section for Specifics

Turbolizers

Centralizers

Guide & Float Shoe

CitationsPage 3) Neal Adams Drilling Engineering: A Complete Well Planning ApproachPage 4) Texas Water Development Board WebsitePage 6) Peeler # 1 E-Log Drilled By Aurora Resources CorporationPage 8) Baker Hughes Mud Program Quintanilla EFS 1-H, Drilled by Aurora Resources CorporationPage 10) Baker Hughes Cement Proposal Quintanilla EFS 1-H, Drilled by Aurora Resources Corporation.Page 12) Texas RRC Rule 3.13 and discussions with James Huie, District 1 & 4 DirectorPages 13-14) Antelope Oil Tools catalog

All other recommendations are solely based on B. Scott Hines’s experience as Drilling Engineer and accepted drilling practices. They are not meant to superceedany companies policies or guidelines.