Integrated Simulation for Hydraulic Fracturing, Productivity Prediction, and Optimization in Tight Conglomerate Reservoirs

Abstract

With the development of advanced horizontal drilling and multistage hydraulic fracturing techniques, the productivity of unconventional tight oil such as that found in the Baikouquan Formation of the Mahu Sag in the Junger Basin has been increasing. The Mahu oilfield is the largest tight conglomerate reservoir in the world. However, predicting the productivity of fractured horizontal wells in tight oil remains a challenge due to the high heterogeneity of the reservoir and complexity of its hydraulic fractures. Therefore, this study proposes a workflow for coupled geological modeling, along with fracturing and reservoir simulations in tight conglomerate reservoirs. Taking well block Ma131 as an example, a three-dimensional geological model is first built according to the results of geophysical research. The unconventional fracture modeling is used next to establish a fracturing simulation. Given the lack of natural fractures and the high concentration of conglomerate in the study area, the method of the multiple groups of microscale natural fractures is used to simulate the impact of gravel on fracture propagation. The feasibility of the method is verified with microseismic monitoring data and treating curves. Thereafter, an unstructured grid and the INTERSECT reservoir simulator are used to simulate the production performance of horizontal wells. The stress sensitivity effect of the rock matrix and fractures and the changes in the formation flow field caused by fracturing are considered in the reservoir simulation. Hydraulic fractures are found to be unable to form complex fracture networks easily under the conditions of high stress difference, high gravel content, and undeveloped natural fractures. However, they show the characteristics of macroscopic simplicity and local branching. Reducing cluster spacing can increase the complexity of hydraulic fractures and the productivity of horizontal wells. Finally, the proposed integrated simulation process is used to optimize well spacing, fracturing stimulation parameters, and the production system. Overall, the study serves as a guide for maximizing the production and economic benefits of tight conglomerate reservoirs.