An Extraordinary Drilling Challenge in the Rocky Mountain Overthrust Belt
- J.D. Swanson (Arco Oil and Gas Co.) | I.M. Brandt (Arco Oil and Gas Co.) | R.D. Johnston (Arco Exploration Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling Engineering
- Publication Date
- March 1987
- Document Type
- Journal Paper
- 75 - 85
- 1987. Society of Petroleum Engineers
- 1.6 Drilling Operations, 1.10 Drilling Equipment, 1.1 Well Planning, 1.11 Drilling Fluids and Materials, 4.1.9 Tanks and storage systems, 5.1.2 Faults and Fracture Characterisation, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.1.6 Hole Openers & Under-reamers, 1.6.1 Drilling Operation Management, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.14.1 Casing Design, 1.6.10 Running and Setting Casing, 1.14 Casing and Cementing, 1.11.4 Solids Control
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Summary. The rugged northwest Wyoming overthrust presented a significant drilling challenge. The evaluation of the Madison formation below 16,500 ft [5029 m] in the Broad Canyon No. I exploratory well was the culmination of 6 years of drilling activity in the area. Two previous wells, drilled from essentially the same location, failed to reach the Mississippian objective and were abandoned after numerous drilling problems. Drilling through the Madison objective was completed on the problems. Drilling through the Madison objective was completed on the third well, Broad Canyon No. 1, after 500 days of continuous operations. The setting and cementing of deep, large-diameter casing strings and the eventual drilling of a liner through a plastic flowing evaporite zone highlighted the successful drilling program.
We began operating along the Greys River Road in the Bridger Teton Natl. Forest in early 1978 (see fig. 1). Corral Creek No. 1-29, the first well we drilled in the area, encountered numerous drilling problems including severe deviation and hole instability. After four major fishing jobs, Corral Creek No. 1-29 was plugged and abandoned at 13,937 ft [4248 ml after 444 days of continuous drilling operations. Fig. 2 shows the drilling-time curve for this initial exploratory well.
Marten Creek No. 1, our second well in the area, was then proposed as a deeper, 17,500-ft [5334-m] Mississippian test. This well, located I mile [1.6 km] east of Corral Creek No. 1-29, encountered shallow lost circulation in addition to the hole instability and deviation problems experienced in the previous well. This well also problems experienced in the previous well. This well also drilled into a plastic flowing evaporite section that generated four fishing jobs and subsequent sidetracks. Marten Creek No. 1 was prematurely plugged and abandoned at 13,154 ft [4009 ml after 467 days of drilling operations. Fig. 3 shows the drilling-time curve for this second unsuccessful exploratory well.
Immediately after the plugging of Marten Creek No. 1, planning began on the third well in the immediate area, Broad Canyon No. I (located about 100 ft [30 ml away from the abandoned Marten Creek No. I wellbore). Because of problems encountered in the previous wells, a task force was formed to define the problems and then to recommend a plan to overcome the difficulties in drilling Broad Canyon No, 1. This paper presents a case history for this challenging exploratory well.
Broad Canyon No. I was proposed to drill through the Prospect thrust plate to test the subthrust Mississippian Prospect thrust plate to test the subthrust Mississippian Madison. From Marten Creek No. I and Corral Creek No. 1-29, fairly precise geologic control was available to about 13,000 ft [3962 m]. Although neither of these wells penetrated below the Prospect thrust, underlying formations were expected to continue as a normal section. Fig. 4 shows the proposed geologic cross section for Broad Canyon No. 1 and the two prior offsets, along with a generalized stratigraphic column for this area. Also included are drilling problems associated with each interval encountered by these wells.
Broad Canyon No. I was projected to drill through the Darby thrust and into the overturned limb of a folded Cretaceous interval. These highly disturbed beds were expected to be extremely unstable because of high dip angles, fluid-sensitive shales, and massive associated coal beds. Below the inflection point of the fold, normal Cretaceous formations-which have significantly greater stability because of lower dip angles and rock stresses-were anticipated. Under the Cretaceous, Jurassic and Triassic formations were expected to continue to the Prospect thrust and the Thaynes-Woodside evaporite zone. This interval presented very serious drilling problems in both earlier wells. The formation contained highly bentonitic shales, anhydrites, halites, and polyhalites, all interbedded in thin stringers. In addition, as a result of the high tectonic stresses associated with overburden and the Prospect thrust, the zone exhibited a plastic flow condition with Prospect thrust, the zone exhibited a plastic flow condition with extremely high shear forces and rapid movement into the borehole. Formations below the Thaynes-Woodside evaporite were then thought to continue in normal sequence, as shown in Fig. 4.
Preparations for planning Broad Canyon No. 1 were Preparations for planning Broad Canyon No. 1 were actually begun before final plugging of Marten Creek No. 1.
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