Explosive Termination of a Wild Well Evaluation of a Concept

Abstract

A concept to terminate a wild well by detonating a subsurface explosive charge placed in a relief well near the wild well has been investigated and found to be feasible. The study described in this paper dealt with the application of conventional chemical explosives; however, the concept is equally valid for nuclear explosives. Introduction In March, 1970, the Shell Cox No. 1 well near Jackson, Miss., blew out during drilling, caught fire, and eventually cratered and extinguished itself. The well was a 22,000-ft high-pressure sour-gas well. Flow rates while the well was blowing out were estimated to range from 20 to 100 MMcf/D. Data gathered on site indicated that the crater had plugged at a relatively shallow depth, causing an underground blowout. Plans were developed to drill a relief well to total depth. Drilling time of this well was estimated to be 12 to 18 months. The great depth, the directional drilling problems, the presence of sour gas, and the tightness of the formation were severe conditions that dictated the development of a novel concept to kill the well quickly. Two such concepts were developed. The first consisted of (1) drilling an intercept well to a depth of approximately 10,000 ft in such a way that the casing in the intercepting well was in contact with the casing in the Cox No. 1 well, (2) cementing the two strings together, (3) perforating the strings to create communication, and (4) pumping cement into the wild well to kill it. This is the technique that was eventually used. The second concept consisted of (1) drilling a 10,000-ft intercept well converging to within 15 ft of the wild well, (2) washing a large cavity at the bottom of the hole, (3) pumping conventional explosives into the cavity, and (4) detonating on command. The explosion would create a larger cavity, crush and rubble the rock, collapse and shatter the casing in the wild well, and stem the flow of gas at that depth. The purpose of this paper is to discuss the program that was carried out to evaluate this concept. Calculations, using finite-difference programs, were made to evaluate the effect of explosive properties and rock properties on the cratering and ground motion associated with the detonation so that the shot could be properly designed. In addition, an explosive formulation was developed that met the requirements for safe handling and pumping on the surface and detonation in a high-pressure and high-temperature environment. From the study it has been concluded that the concept of using explosives to terminate a wild well is feasible. Although the concept is untried to date in this country, the Russians have demonstrated the soundness of it by killing two wild gas wells using nuclear explosives. Project Planning Project Planning After the explosive kill concept was conceived, the following program was developed to evaluate it and to bring it to completion, if necessary. Phase 1 Determine the feasibility of explosively terminating Cox No. 1 and develop specific proposals to accomplish the job. JPT P. 1084