Optimizing Sandstone Matrix Stimulation in HT Well 'X' (A Case Study)

摘要

Pakistan's demand for natural gas is quickly outstripping supply and the crisis is a symptom of a much larger problem destined to cause consumers even greater pain in the future. In this picture every MMscf of gas is not only important for the country but also important for OMV, which is fueling Pakistan for more than 20 years. OMV is trying hard to meet the demand by restraining the decline in currently producing fields and to develop unconventional resources. In one of OMV operated fields, after watering out 3 wells, well 'X' was the only one available to feed 13 MMscf gas per day to processing plant to keep it alive. To increase the recovery from reservoir, well 'X' was put on wellhead compression in March 2012 subsequently rapid decline rate (1.09 MMscf/month) was observed; finally production drop to 7.8 MMscfd which was alarming to shut down the complete plant below 6 MMscfd. The production modeling using commercial package depicted the skin of +16 in well 'X' which was not supported by available hard data. The interpretation of last buildup data was not strengthening the idea of near wellbore damage, further the reservoir pressure used was dubious as it was taken ~1 year ago. Two cores were available in well 'X'; unfortunately none was from sandstone producing interval. As an analogy two core plugs from nearby well were sent for XRD analysis & core flow test was performed with specially designed organic clay acid for high temperature reservoirs (OCA-HT). Based on encouraging core flow test outcomes, an optimum job volume was engineered considering the critical zones radius (up to 1 ft), in fear for fine migration & water producing zone. Matrix stimulation job was executed in October 2012 which resulted in increment of ~7 MMscfd extending the plant life beyond 1 year. This paper describes the complete case study of optimizing the matrix stimulation in high temperature sandstones. Furthermore it will show how results achieved so far are promising which added a reasonable value to the producing asset and saved huge revenue loss to the company.