Well selection optimization verification of large scale compound acid fracturing in carbonate fracture-cavity reservoir in Tahe oilfield

The large scale compound acid fracturing is a new type of acid-refracturing treatment technology propounded for the wells with no or low potential production after conventional acid fracturing in carbonate fracture-cavity reservoir in Tahe Oilfield. The new technology has made the production of few no potential wells or low production and low inefficiency wells promoted or recovered, and the whole effect of production enhance is evidence with some difference. Based on the systematic analysis on previous features of reservoir and acid-fracturing effect before large scale compound acid fracturing, this paper optimizes and proposes the geological well selection principle for large scale compound acid fracturing. The analysis results indicate that the wells for efficient large scale compound acid fracturing should be located in these places, where the favorable positions of oil and gas is accumulated, or seismic attribute characteristics are better than others（high change rate amplitude or large scale of reflect body）; besides, the reservoirs which have no effectively connection during the past conventional acid fracturing and wells with insufficient energy, low production（low cumulative production）poor effect water-flooding are also suggested. Last but not least, the wells should be primarily selected which are under the above mentioned geologic condition with further far distance from the centre of reservoir.