Optimization of Stimulation Treatments in Medium-Permeability Gas/Condensate Reservoirs Using Real-Time Downhole Data Acquisition With Novel Technology of Permanent Sensors

摘要

Development of light-oil fields in Mexico is part of a strategic program to increase overall production in Mexico. Among the light-oil fields, operators have gas condensate carbonate reservoirs with medium permeabilities ranging from 3 to 10 md, with very high drawdowns. The initial development concern was how to make them produce above the bubble point. The first thought was to fracture the intervals to reduce the drawdown, but the permeability values from well tests made matrix stimulation appear acceptable. Some believe that with permeabilities in the 3 to 10 md range, fluid-loss issues may prevent reaching fracture pressure. In that case, a matrix treatment may be used, thus avoiding a more expensive hydraulic-fracture treatment. However, step-rate test (SRT) results were unclear, so doubt remained. In three cases, permanent downhole sensors were available, and minifrac and fall-off analyses with downhole data were possible. Observation of the flow regimes in the data established a comparison of planned flow periods before and after the tests and frac jobs. If this data is used to help optimize treatment, applying frac treatments will be the best choice, and the investment will be justified. It was also observed that lower injection rates must be applied during the SRTs, starting from 0.5 bbl/min. The operator concluded that “gray zone” candidate wells with medium permeabilities can benefit from matrix treatments and fracture treatments. Post-fracture evaluation shows that drawdown matches very closely to the flow prediction, and this kind of reservoir can be produced above saturation points. In this paper, three successful case histories are discussed in detail.