A new fracturing technology of intensive stage + high-intensity proppant injection for shale gas reservoirs

Abstract

So far, large-scale development of shale gas wells above 3500 m in the Changning Block of the Sichuan Basin has been realized by means of the large-scale hydraulic fracturing technology. As the main process parameters are finally set, however, the improvement rate of its stimulation effect tends to slow down, while in North America, single-well production has increased significantly by shortening cluster spacing and increasing proppant volumes. In order to provide a reliable practice basis for optimizing the parameters of shale gas fracturing process, this paper analyzes the productivity increasing mechanism of the new fracturing technology of intensive stage + high-intensity proppant injection by virtue of the model for calculating induced stress and multi-stage and multi-cluster productivity of horizontal wells. And accordingly, the main engineering factors of fracturing stimulation technology were ascertained. Then, after the pilot test scheme on this new fracturing technology was formulated according to the geological parameters of this block, the pilot test was carried out. Finally, the fracturing process parameters were optimized based on actual production effects and experimental results. And the following research results were obtained. First, shortening the spacing between main fractures, increasing the interference degree of induced stress and improving the stimulation degree of hydraulic fractures to shale reservoirs are the technical keys to the intense stage, and increasing the proppant volume, reducing the influence degree of proppant embedding and breaking on the attenuation of fracture conductivity and ensuring the long-term conductivity of propped fractures are the internal causes of significant production increase through high-intensity proppant injection. Second, the optimized implementation parameters of this new process in the Changning Block are as follows. The cluster spacing is in the range of 15–20 m, the proppant injection intensity is 2.0–2.5 t/m, and the liquid consuming intensity is 30–35 m3/m. It is concluded that this new process increases the single-well production of shale gas wells and the development benefit of the Changning Block and provides technical support for improving the comprehensive development benefit of shale gas wells in this block.

Topics & Concepts