Integrating a Boundary Element Method Based Hydraulic Fracturing Simulator with a Compositional Reservoir Simulator for Well Lifecycle Simulations

Abstract

ABSTRACT In this paper we present an integrated DDM-based hydraulic fracturing-compositional reservoir simulator that can simulate each phase in the lifecycle of a hydraulically fractured well from hydraulic fracturing to shut-in, to flowback/production and gas huff-n-puff improved oil recovery. The new model is first bench marked against our in-house fully 3-D model of a penny-shaped propagating fracture by comparing the width distribution and fracture geometry. Then, the model is used to simulate production from complex fracture networks in 3-D. The results show that the reservoir drainage area is constrained by the geometry of the fracture network. The impact of pre-existing natural fractures is investigated by propagating a hydraulic fracture with and without natural fractures and conducting production from the propagated fracture networks using the compositional simulator. The results show that: (1) natural fractures can enhance well productivity from a more compact reservoir region closer to the production well, and (2) it is important to use realistic natural fracture geometry models for history matching well production. Finally, to illustrate the model capabilities, the model is used to investigate well drawdown strategies. Results show that aggressive drawdown strategies can be used in rocks with low clay content. INTRODUCTION Hydraulic fracturing and horizontal drilling have been employed to unlock oil and gas resources from unconventional reservoirs, including naturally fractured formations. To achieve the maximum oil and gas recovery from the subsurface, a model is needed to provide guidance on fracture treatment design and production for a well lifecycle. However, most current fracturing simulators and reservoir simulators are separate from each other, which results in restrictions for how they can be used to simulate different phases in the life of a well. In this paper, a novel fracturing-reservoir simulator is presented by integrating the displacement discontinuity method (DDM)-based hydraulic fracturing simulator with a compositional simulator for a naturally fractured formation. Many techniques have indicated the existence of pre-existing natural fractures, such as fiber optic-based sensing, microseismic evaluation, pressure interference analysis, geochemistry analysis, and slant core wells (Cao and Sharma, 2022a; Ciezobka, 2021; Zhang et al., 2022). The presence of natural fractures can result in the formation of complex fracture networks, such as at Hydraulic Fracturing Test Site #1 (HFTS #1) and HFTS #2 (Bessa et al., 2021; Cao et al., 2023; Cao and Sharma, 2023a; Gale et al., 2021; Pudugramam et al., 2021; Shrivastava et al., 2018). Since these complex fractures can have a direct impact on the productivity of an unconventional reservoir, it is important to accurately capture the formation of propagated fracture networks with pre-existing natural fractures.