The Mangala oil field contains 27-30°API waxy, low GOR crude oil, with a wax appearance temperature within 5°C of reservoir temperature (60-63oC) and a pour point above 40°C. To meet the flow assurance challenges for such paraffinic crude, jet pumping with hot water at 85°C as power fluid is the first choice for an artificial lift system. Power fluid surface injection pressure is designed to be 3,000 psi. Wells are expected to produce up to10,000 barrels per day of oil or oil and water.

High temperature, high pressure power fluid in the annulus means that the completion string will be exposed to high external pressures and variations in the casing/tubing temperature profile during the life of the well. High compressive forces, the potential for collapse, wellhead growth and the extreme case of anticipated helical buckling make the well completion design quite challenging. It is important that the well completion design is capable of withstanding such conditions. The accurate representation and prediction of casing/tubing temperature, pressure profiles and loads in the casing/tubing during all well operations including jet pumping are crucial to assess the integrity of the completion string.

This paper describes the anticipated loads during the well life, and use of a wellbore thermal simulator, and tubular stress analysis software program to simulate the potential stress loads. This helped optimise the design of the casing and tubing strings to anticipate and foresee and avoid potential problems like connection leaks, permanent tubing buckling, packer load requirements, etc.

You can access this article if you purchase or spend a download.