Research on Geological-Engineering Integrated Fracturing Design Method for Exploration Reservoir Stimulation in Qaidam Basin

Abstract

As oil and gas exploration in the Qaidam Basin continues to advance toward deep and unconventional domains, reservoir fracturing stimulation is confronted with increasingly severe challenges. Target reservoirs are generally characterized by complex geological conditions, high temperature and high pressure (HTHP), and strong heterogeneity, leading to issues such as “difficult formation fracturing initiation and poor proppant placement” during construction, which significantly restrict the stimulation effect and exploration benefits in key exploration areas. To systematically address this challenge, based on the statistical analysis of fracturing construction data from nearly 900 layers in the basin, it has been clarified that difficult-to-fracture reservoirs feature deep burial, abnormally high fracture pressure gradients, and relatively low porosity. Through in-depth analysis, the underlying causes of high formation fracture pressure have been revealed, mainly including significantly high in-situ stress coefficients, low reservoir porosity, well-developed bedding structures, and severe near-wellbore pollution. Targeting the aforementioned causes, a fracturing design method system centered on “geological-engineering integration” has been proposed. This method establishes high-precision 3D geological and geomechanical models, takes the “Unconventional Complex Fracture Network Model” as the framework, and conducts scientific staged and clustered optimization, fracturing fluid system selection, and fracture propagation morphology optimization. The integrated design method has achieved remarkable results in the exploration practice of the Qaidam Basin, successfully guiding the completion of fracturing construction for 24 wells and 34 layers with a construction success rate of 97.8%, effectively facilitating 19 layers to obtain industrial oil and gas flow. The research results have established a set of key fracturing design technologies suitable for highly heterogeneous and abnormally high-pressure reservoirs, providing important technical support for the beneficial exploration and effective development of the Qaidam Basin and similar complex oil and gas reservoirs.