Study and Application of Volume Fracturing Technology in Tight Sandstone Gas Reservoir of the Y Block

Abstract

To address the challenges of the Xujiahe tight sandstone gas reservoir in Block Y and explore suitable volume fracturing techniques for tight sandstone gas, hydraulic fracturing simulation experiments with full-diameter core were conducted using sandstone samples taken from the Y Block. Those can reconstruct the three-dimensional morphologies of hydraulic fractures with various parameters, confirming that the induced fractures were predominantly single fracture. Based on the previous well construction insights and fracturing software simulation results, key parameters such as reservoir stimulation scale were determined, and a pilot test was conducted. The research indicated that, according to the development characteristics of the Xujiahe tight sandstone gas reservoir in Block Y, an optimized strategy of “sweet spot precise stratification + fracture height control to avoid water + high-intensity sand addition” was adopted. Specifically, for the vertically developed multiple sub-layers from Xu2 to Xu6, technologies such as multi-cluster fracturing within stratified layers, in-layer flow restriction, and temporary plugging between layers were employed to ensure thorough vertical stimulation. Given the overall tightness of the reservoir, underdeveloped natural fractures, and significant physical property differences among the sub-layers, stratified and reasonably optimized construction scales and parameters were adopted, with a focus on creating long fractures and utilizing “high-rate injection + preflush slickwater” to form a small number of branch fractures, thereby enhancing the stimulated volume. To address the water issue in the lower part of the Xu2 reservoir, simulations of fracture propagation heights under different injection rates were conducted to select the optimal fracture height, ensuring a safe distance between the fracture bottom and the water layer. Field test on the YS6 well which underwent fracturing of three layers with ten clusters, with a sand addition intensity of 3.6 m3/m, an average sand-to-fluid ratio of 1:12, and a volume stimulation mode characterized by less fluid and more sand. After fracturing, the well tested at a daily gas production rate of 13.5×104 m3, significantly increasing single-well productivity. The research findings provide a valuable engineering insight for future volume fracturing of similar reservoirs in the Y block.