Non- Coiled Tubing Stimulation of Water Injectors

Abstract

Abstract Sea water is injected to maintain the reservoir pressure that supports the oil production from carbonate and sandstone reservoirs. The Gulf sea water contains more than 4000 ppm sulfate and the formation contains more than 19000 ppm calcium, this will cause calcium sulfate precipitation at the reservoir conditions. The precipitate at the reservoir conditions will be anhydrite and it will cause formation damage that will reduce the well injectivity. Stimulation treatments are required to recover the well injectivity and this requires stopping water injection to perform the stimulation treatments. In this study we are proposing a new method that we can use to stimulate water injectors without stopping the water injection. The new method includes adding a chelating agent to the injected sea water at the well head at 15 wt% concentration. Several solubility and coreflooding tests were performed using actual carbonate cores and the new chemical at different temperature ranges. The chemical injection does not need coiled tubing and can be injected at the surface with the sea water. The chelating agents will sequester all calcium in solution and will prevent the calcium sulfate precipitation. The chelating agent used in this study is GLDA. Solubility tests up to 250°F at high pressure showed that the GLDA is stable with the sea water. Coreflood experiments and CT scans showed the ability of GLDA in the creation of nice wormholes through a 6 in. and 1.5 in. carbonate cores at 100 and 70°C respectively. The GLDA chelating agent can be used to stimulate sea water injectors without any additives as this chemical is stable and is gentle with the well tubulars. Previous corrosion studies on GLDA showed that its corrosion rate is in the allowable range without adding corrosion inhibitors.