Solid Expandable Solution to Qualify Existing Non-Sour Service Production Casing

Abstract

In the early development of the Eagle Ford Field in South Texas, the initial well design equipped wells with non-sour service P-110 production strings. After the early stages of production, some of these early wells were found to produce increasing levels of H2S, which posed the problem of potential sulfide stress cracking at shallow wellbore depths because of relatively high H2S partial pressures and associated low formation temperatures (<145°F). To mitigate this risk, production packers were run to protect the production casing in flowing wells with H2S partial pressures of more than 0.05 psi. As these wells were depleted to lower flowing pressures, production was maintained by intermittently producing. This method was used because of limited or no artificial lift options for wells with non-sour-service production casing. A solution allowing artificial lift was needed to better maintain and sustain production, to extend the utility of these wells, and to allow future recovery of the potential reserves.

Expandable casing technology was ultimately chosen as a solution to maintain well integrity and enable implementation of artificial lift (gas lift). This operation involved the running of an expandable liner to cover and protect the section of the casing susceptible to sulfide stress cracking. A solid expandable tubular designed to support the corrosive environment was successfully tested and qualified for sour service in extreme corrosive conditions by the operator metallurgists, adhering to sour service qualification according to paragraph A.2.1.6 and Annex B of NACE MR0175/ISO 15156 standards.

Additional testing was performed to ensure that the required length of the chosen liner could be run while being held at surface. Normally, these liners are left free at the top which allows slight shrinkage in length to avoid high tensile forces as the liner is expanded outward. The liner system passed all tests performed independently by the service company. The team proceeded to install the solid expandable liner, from 7,047 ft. (where the temperature was above the threshold of H2S embrittlement) to surface to protect the existing 5 1/2-in. 20 ppf P-110 casing. The internal D-diameter (ID) of the completion changed from 4.778 in. (original production casing size) to 4.140 in. (once the pipe was expanded). The well was then completed with 2 3/8-in. tubing, a production packer, and traditional side-pocket-mandrel gas lift. Currently, the well is producing on continuous gas lift with the casing protected by the expandable liner. The expandable liner provided an enabling solution that allowed implementation of the optimal artificial-lift method to recover additional resources within the drainage area.