Abstract

Gas Production in the Anadarko Basin presents some unique problems as well as some problems correlative with other reservoirs of similar depths and pressures. Some of these problems are inherent with pressures. Some of these problems are inherent with the type of reservoir mechanics encountered. Others are created by drilling and completion methods employed. This paper will deal with El Paso Natural Gas Company's approach to the solution of these problems as knowledge of the area and production problems as knowledge of the area and production technology is improved.

Introduction

El Paso Natural Gas Company has been actively engaged in exploration, drilling, and producing deep high pressure gas wells in the Anadarko Basin since 1971. At present date (January, 1979) the Company has drilled 63 wells in the Basin varying in depths to 23,449 feet. Formation pressures have exceeded 17,000 psig with bottom hole temperatures of 350 degrees F. Due to the success ratio E.P.N.G. has continued its drilling program and presently has 8 rigs operating in the deep Anadarko Basin.

Since this paper pertains to producing deep high pressure gas wells, the drilling, completion, and associated problems cannot be covered; however a typical Morrow pipe program will be described to establish a base for production operations.

COMPLETION

A typical completion is based on the scheduled depth and is normally designed to have a minimum 5" production string. Therefore, the production liner dictates the casing program. production liner dictates the casing program. Normally a 20" or 30" spiral conductor pipe is set at approximately 90 feet and cemented back to surface. The surface string, usually 13-3/8", is then run to 4000 feet and cemented in stages to surface for protection of all fresh water zones. An intermediate casing string, usually 10-3/4", is then set into the Atoka Zone at approximately 12,000 feet for protection of upper weak formations from abnormal pressures. After setting the intermediate string, a 7-5/8" drilling liner is set in the top of the Upper Morrow shale at approximately 14,000 feet in preparation for the abnormal pressures that normally occur when drilling the Morrow formation. After the drilling liner is set and a good cement bond is established, the well is drilled through the expected producing zone. Then the production liner is run, a tieback adapter is available should a tie back string be deemed necessary. Should the situation warrant, a tapered production string may be run instead. A good production string may be run instead. A good cement bond on the drilling and production liner is essential, therefore tests must be conducted to assure a proper bond. After tests are completed the hole is displaced with brine water in several stages depending on mud weight and several viscous pills are used to assure that the hole is clean. pills are used to assure that the hole is clean. The polished bore receptacle is then dressed and another circulation made prior to laying down the drill pipe. The tubing is then run, usually 3-1/2", and the annulus is displaced with 10 PPG treated brine water to serve as a packer fluid. When spaced out the tubing is landed in the polished bore receptable. Compression is set to allow polished bore receptable. Compression is set to allow pre-calculated seal movement of the tubing string pre-calculated seal movement of the tubing string during subsequent treating and production operations. Moving seals may fail, so it is extremely important that the correct compression is set the tubing to allow minimum seal movement. (Figure 1).

WELL HEADS

Formation pressure dictates well head design. When dealing with surface pressures of 10,000 psia to 14,000 psia, well head equipment must be adequate to safely control future operations.

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