A Decade of Drilling Innovation and Progress in the Paris Basin
- D.B. Canter (Esso Rep) | J.-M. Simon (Esso Rep)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling Engineering
- Publication Date
- March 1991
- Document Type
- Journal Paper
- 65 - 70
- 1991. Society of Petroleum Engineers
- 5.5.2 Core Analysis, 5.6.2 Core Analysis, 1.6.2 Technical Limit Drilling, 1.6.6 Directional Drilling, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 6.5.3 Waste Management, 1.6.1 Drilling Operation Management, 1.11 Drilling Fluids and Materials, 1.6.9 Coring, Fishing, 1.12.6 Drilling Data Management and Standards, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.7 Pressure Management, 5.2 Reservoir Fluid Dynamics, 5.8.7 Carbonate Reservoir, 1.6 Drilling Operations, 1.5 Drill Bits, 5.6.1 Open hole/cased hole log analysis, 5.3.4 Integration of geomechanics in models, 5.6.4 Drillstem/Well Testing
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Since 1979, Esso Rep has drilled more than 150 exploration and development wells in the Paris basin. A cost-per-foot reduction of more than 40% was achieved despite a near doubling of rig rates. This paper discusses the unique directional drilling approach used and the drilling, formation evaluation, and contracting techniques.
Esso Rep has drilled more than 60 exploration and 90 development wells in the Paris basin during the past 10 years. For environmental and economic reasons, almost all development wells were directionally drilled from multiwell surface clusters. Most of these wells are 8,000 to 10,000 ft [2440 to 3050 m] measured depth (MD) with horizontal displacements of 2,000 to 5,400 ft [610 to 1645 m]. Well targets are usually 200 x 260 ft [60 x 80 m]. Fig. 1 shows a simplified overview of a typical Paris basin development well. The objective is usually the Triassic sands at about 7,400 ft [2255 m] but can also be the Middle Jurassic carbonates at 5,500 ft [1675 m]. The Paris basin is not inherently a difficult area for drilling. The carbonates, shales, and chalks of the Cretaceous and Jurassic vary from fairly soft to only medium hard. Abnormal pressure is not a problem in the area, and formation dips are moderate and consistent. Drilling problems include lost circulation, which is fairly common and can be severe if mud weights are not controlled carefully in surface hole. In addition, the shales of the lower Jurassic are very water-sensitive and require use of an inhibitive mud.
Over the last decade, average Paris basin well time has been cut from 52 to 20 days/well. There are five main reasons for this improvement. 1. Use of a unique computerized statistical approach to directional drilling cut overall directional control time in half. 2. Extensive field trials to determine the optimum polycrystaline-diamond-compact (PDC) bit, to maximize run length, and polycrystaline-diamond-compact (PDC) bit, to maximize run length, and improve rate of penetration (ROP) led to runs of 2,900 ft [885 m] and ROP's of 85 ft/hr [26 m/h]. 3. Formation evaluation guidelines for exploration drilling halved the rig time devoted to formation evaluation while still ensuring the collection of all essential data. 4. Drilling with underbalanced oil mud in some zones above the reservoir improved ROP by 60% and eliminated hole problems. 5. Consistent use and frequent updating of footage and lump-sum incentive contracts resulted in significant and continuous improvement in overall drilling performance. Of these five items, only the statistical approach to directional drilling was unique and innovative when developed in the early 1980's. The other four performance-improvement techniques were already well-known throughout industry, demonstrating that concerted application of familiar ideas still can generate significant improvement in drilling performance. Each of the five performance improvement methods is discussed in more detail below.
Directional Drilling Method. In directional drilling, experience is sometimes more valuable than theory. Many operators have developed theory-based software to predict how a specific bottomhole assembly (BHA) should perform in terms of build and walk rates under given conditions-weight on bit (WOB), bit rotation velocity, hole angle, etc. Directional drilling data from past wells in an area, however, can be used to generate an experience-based prediction of future BHA performance that is sometimes more prediction of future BHA performance that is sometimes more accurate for that specific area than the theory-based prediction.
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