Abstract

For several years, the author has participated in the design and installation of equipment for many deep Anadarko Basin wells, including the two deepest wells ever drilled. Most of the early Anadarko deep completions featured large OD production tubing, anticipating high productive well capacities; but more recent completions have been made with smaller 2 7/8" OD tubing, and the problems of tubing stress are quite serious. For instance, well shut-in pressures may reach to over 12000 psi. Fracturing with proppant may require surface tubing pressures of over 17000 psi. These types of problems will be discussed and successful solutions for them are illustrated.

High pressure casing and tubular prices, and recent shortages of some tubulars, have demanded new approaches to casing and liner design programs. One problem, not unfamiliar to earlier deep drilling problem, not unfamiliar to earlier deep drilling engineers, is the problem of high pressure liner leaks. The use of "liner-top" packers installed after the liner has been cemented, to control this leakage, will be discussed and illustrated. The new methods of equipping these wells will be discussed here for the first time and several installations will be illustrated. Some recent dual completions of high pressure Anadarko wells will be discussed and illustrated.

Introduction

Several years ago, it was common to design deep well completions in the Anadarko Basin with large tubulars, such as 3 1/2 in. OD and 4 1/2 in. OD tubing, for production. Some operators still do this in larger, more productive reservoirs; but most now use 2 7/8 in. OD tubing. When smaller 2 7/8 in. OD tubing is used, combined tubing fiber stress during high pressure operations may be excessive, unless special pressure operations may be excessive, unless special precautions are taken. The tubing shut-in pressures in precautions are taken. The tubing shut-in pressures in some wells exceed 14000 psi. Fracturing pressures have exceeded 17000 psi. Tools must be used which will withstand these pressures and, at the same time, enable the tubing to shorten during treatment without permanent deformation. A way should be provided for permanent deformation. A way should be provided for removal of the tubing, in case of tubing failure, without having to mud up and kill a producing well.

Gas leakage around the tops of liners set through Morrow/Springer formations are common and the liner tops must be sealed to prevent excessive pressuring of the annulus. Liner top packers, which have seal nipples landed into the liner tie-back receptacle and a pack-off seal setting in the intermediate casing, have pack-off seal setting in the intermediate casing, have been used for this purpose, if the leak cannot be squeezed off.

DISCUSSION OF HIGH PRESSURE INTERVALS IN ANADARKO BASIN

Fig. 1 shows how pore pressure and frac gradients vary with depth in a typical Anadarko Basin well. High pressure above-normal gradients begin at approximately 9500 ft., in the Tonkawa formation, and increase with depth to the top of the Morrow sand at approximately 17000 ft.

When low permeabilities are found in the suspense interval from 12400 ft. to the top of the Morrow sand, most operators set intermediate casing in the Morrow shale above the Morrow sand. If permeability is present, intermediate casing is set in the Deese shale present, intermediate casing is set in the Deese shale around 12000 ft. and a drilling liner is set in the Morrow shale around 15800 ft.

The frac gradient often is very close to the pore pressure gradient as the depth of the well approaches pressure gradient as the depth of the well approaches the top of the Morrow sand. When the frac gradient in the primary objective zones is equal to or very close to the pore pressure gradient, a second drilling liner is required to penetrate and complete in the lowermost part of the Morrow/Springer column, usually about part of the Morrow/Springer column, usually about 21000–22000 ft.

The deeper horizons below the Morrow/Springer are not generally considered to be abnormally pressured. There are some high pressure anomalies in the Woodford shale and the Simpson group, however; but the length of this paper does not permit proper discussion of completions below the Springer.

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