Completing High Pressure Gas Wells - Mechanics and Problems

Abstract

Introduction This discussion is limited to high pressure gas wells or wells with abnormal pressure gradients. It does not cover extreme high pressure gas wells such as have been recently completed on the Gulf Coast where shut-in tubing pressures have been recorded in the vicinity of 12,000 psi. It is realized that such wells would probably be of more singular interest; however, since relatively few have been completed to date, the data are very meager. It is the purpose of this paper to review some of the mechanics and problems involved in the completion of high pressure gas wells. Generally speaking, completion practice refers to operations which take place from the time the well is drilled through the productive zones and continues until the well is placed on production. The wells which will be discussed might be termed as medium high pressure gas wells having pressure gradients of about 0.8 psi/ft of depth. Three gas wells in this category were recently completed in the Gulf of Mexico approximately three miles off the Texas coast near Mustang Island. The completion of these wells will be discussed in detail. Casing Program The proper design of casing programs for high pressure gas wells is of utmost importance. This is particularly true of offshore wells where the safety of personnel and equipment is at stake. For this reason the factors of safety must be maintained well within the accepted limits. The program for all three offshore wells followed the same general pattern except for the 5-in. OD oil string. Due to trouble encountered with sticking in the deviated hole, the oil string was swaged to 4.5-in. OD at the bottom of the 7-in. OD casing at approximately 10,600 ft. The typical program is shown in Table 1. Total average weight of tubular goods used in each well was 1,257,000 lb or approximately 628 tons. For the sake of simplicity the details of completion of Well No. A–3 will be discussed since all three wells were completed in the same manner.