DEA-090 Phase IV – Drilling Plastic Shale at Great Depth; A Study to Improve Penetration Rates with Environmentally Acceptable Drilling Fluids

“Drilling Plastic Shale at Great Depths-A Study to Improve Penetration Rates with Environmentally Acceptable Drilling Fluids”

After successfully completing Phase 3, we are actively seeking a minimum of 3 participants prior to starting Phase 4. Busy year end activities have necessitated a re-scheduling of DEA 90 Phase 4 organization meeting to beginning 2003. The objectives and goals are as previously presented to the DEA. Phase 3 had 6 participants. Phase 4 will cost $35,000 per sponsor.

Drilling Engineering Association Project Number:  DEA 90 Phase 4

Drilling Engineering Association Sponsor:  ChevronTexaco Ben Bloys (281) 230-2968

Project Manager:  Alan Black, 801-584-2441 (phone), 801-584-2406 (fax), ablack@terratek.com, TerraTek, Inc., 400 Wakara Way, Salt Lake City, Utah 84108

Project Scope and Objectives:

The objective of this project is to solve the expensive field problem of low penetration rates experienced while drilling with PDC (polycrystalline diamond compact) bits in plastic shales at great depths (high borehole pressures) with water-based fluids.

PDC bits have proven very successful in improving penetration rate in many formations.  The application of PDC bits drilling soft, highly plastic shales at vertical depths greater than 10,000 psi and borehole pressures of 7,000 psi or more with water-based fluids often yielded penetration rates as low at 5 ft/hr.  At the same conditions, roller-cone bits drill at 15 ft/hr.  When drilling the same shale formation at the high  borehole pressure conditions with PDC bits and oil-based fluid, penetration rates of 50-75 ft/hr or greater are possible.

In DEA 90 Phase 1 and 2, the field observations mentioned above were first replicated in full-scale laboratory drilling conditions in Pierre 1 shale at 7500 psi borehole pressure with PDC and roller-cone bits and with water-based and oil-based fluids.  Following verification that field observations could be duplicated in the laboratory, a series of high pressure drilling tests were conducted with different drilling fluids, fluid additives and new PDC bit designs over a range of drilling conditions (WOB and RPM) to determine the mechanism causing the low penetration rates and to evaluate ways to improve penetration rates.  In addition, a study of the effect of shale properties on penetration rate was carried out in various shales and a correlation determined.  Several proper drilling practices have also been determined.  The total number of high pressure drilling tests conducted in DEA 90 Phase 1 (22) and Phase 2 (27) include the testing of eleven different water-based fluids, six different drilling fluid additives (ROP enhancers), one baseline PDC bit and three new PDC bit designs.  The baseline water-based fluid is a 12 ppg NaCl/PHPA with 45 ppb rev dust (simulated drill solids).  All other drilling fluids have also been 12 ppg with the same simulated drill solids.

Phase 3 is investigating effects of drilling fluid density on ROP for different fluids and fluids additives, the percentage of ROP enhancers required to maintain improved ROP and other factors such as the effectiveness of ROP enhancers over time to achieve sustainable ROP’s. 12 high pressure drilling tests have been conducted in DEA 90 Phase 3 and two more are expected for PEMEX by April 2002. A kick-off (planning) meeting was held end March, 1999. A first series of drilling tests were successfully conducted with ROP enhancers and results reviewed with the participants at an August, 1999 meeting hosted by Shell in Houston. Additional tests were conducted in November and a progress meeting was held with the participants on March 14, 2000 at BP Amoco’s facilities in Houston. Then two companies joined the program early ‘00 (MI, then Texaco) based on the successful ROP demonstrations in shale with additives. The program continued its testing program during 4Q ’00 and both the Baroid and MI additives were evaluated during drilling of shale at simulated depth conditions. ExxonMobil joined this program early ’01 (tests completed successfully) and finally PEMEX joined late 2001, thus two additional tests with a 14 ppg silicate mud are planned before commencing Phase 4.

Phase 4 plans to take developments and lessons learned from the first 3 phases to test additional high performance PDC bit designs and optimize the performance in drilling plastic shale with additional ROP enhancers (developed by the fluid companies) in weighted muds. Technology transfer will be facilitated through sharing of sponsoring operator and supplier experiences with drilling shale at high downhole pressures. Current sponsors also recommend in part the study of shale drilling performance at optimized conditions in order to effectively correlate and/or apply learning to their own operations. Additionally, DEA 90 Phase 4 plans to compile developments which have resulted from DEA 90 testing at TerraTek and ensure basic learnings (e.g. bit balling principles, qualitative models) are transferred to sponsors.

Project Deliverables:

Progress reporting at periodic planning and review meetings and a comprehensive final report summarizing all findings, including raw computer files, photos, etc.

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Expected Benefits to the Industry:

Practical field solutions and guidelines for applying this technology to improving penetration rates and reducing drilling costs in shale formations at high borehole pressure conditions is targeted for the DEA 90 Phase 4 project.

Time Scale, Project Cost, Amount per Participant and Number of Participants:

The project will be completed in 18 months. The project requires minimum funding of $105,000 (3 participants). Existing Phase 3 participants include BP, ChevronTexaco, ExxonMobil, Geodiamond/MI, Halliburton/Baroid, Shell, and PEMEX. The cost of DEA 90 Phase 4 will be $35,000 and anticipated start date is mid 2002.