Method for predicting oil-gas productivity before oil testing in ultra-deep dolomite reservoirs

The Cambrian ultra-deep dolomite reservoirs in Tarim Basin exhibit strong heterogeneity and complex reservoir spaces, posing challenges in identifying fluid properties. Low oil-gas production during oil testing and prolonged testing cycles hinder the exploration and development process. By collating well logging and testing data of 14 oil testing layers from 9 wells, the well logging response characteristics of tested interval in the Cambrian dolomite reservoirs were statistically analyzed, parameters and evaluation values closely related to hydrocarbon saturation were identified, and criteria for evaluating hydrocarbon saturation in the reservoirs were established. Well logging parameters related to reservoir productivity were clarified, and by fully considering the impacts of formation pressure, reservoir characteristics, structural development, and acid fracturing, a method for forecasting the productivity in the Cambrian pre-salt dolomite reservoirs before and after acidification was developed. This method was applied in evaluating the hydrocarbon saturation of 10 layers in the ultra-deep Cambrian dolomite reservoirs in Tarim Basin, with a conformity rate of 90%, resulting in a doubling of oil and gas production during oil testing. Productivity prediction was performed in 12 layers using this method, with prediction errors for 9 layers within 15%. Among them, for layers where the difference in productivity prediction before and after acidification was minimal, the testing cycles were reduced by 50%, while for other layers, testing cycles were estimated to reduce to approximately 90% of the current duration. This method can be widely promoted and applied in the ultra-deep Cambrian promoted reservoirs in the Tarim Basin.