Remedy of Sustained Casing Pressure in φ244.5 mm Casing Annulus in South Oilfield of Iraq

Sustained casing pressure was encountered when cementing the wells penetrating abnormally high-pressure salt/gypsum formations in the Halfaya Oilfield and the Missan Oilfield in the south of Iraq. The sustained casing pressure was in a range of 0.69-17.24 MPa, seriously affecting the later development of the oilfields. A curable epoxy resin was used to solve this problem. Laboratory test was conducted to evaluate the thickening time, compressive strength and rheology of the epoxy resin fluid. The test results showed that by changing the concentration of the solidifying agent in the epoxy resin fluid, the thickening time of the epoxy resin fluid can be adjusted between 100 min and 500 min, the 48-hour compressive strength of the epoxy resin fluid can be greater than 50 MPa, the flow index of the epoxy resin is greater than 0.94, and the consistency coefficient is less than 0.10 Pa·sⁿ. In field operation, the epoxy resin was squeezed and injected stepwise into the well and plug it. The total volume of epoxy resin fluid used was more than 100 L and the plugging operation with epoxy resin was done for three times in three wells. After 72 hours of squeezing the epoxy resin, the wellhead pressure was reduced to zero. Using this method, the sustained casing pressure in the φ244.5 mm casing annulus encountered in the south oilfields of Iraq was successfully solved. This technology can be used to solve similar sustained casing pressure problem.