A New Fracturing Reservoir Simulation Model of Tight Low Permeable Fractured Gas Reservoir
Authors: Yang Z. , Li Y. , Zhang L. , Tang S. , Xu X. 
Published: March 2010

This paper presents an improved new reservoir simulation model. By applying reservoir engineering, numerical simulation, and fluid flow theory through porous media to the conditions of production engineering, and taking into consideration the triple medium of matrix, natural fracture, and hydraulic fracture for tight low permeable fractured gas reservoirs, the authors arrived at a comprehensive conclusion for the low non-Darcy and high non-Darcy flows. A corresponding solution model is also presented, made available through computer programming. The results derived from the fracturing reservoir software, developed specifically in this study for tight low permeable fractured gas reservoirs and which takes into account such various aspects as the direction of and influence of in situ stress, reservoirroperties, natural fracture system, and hydraulic fracture length, show that the fracturing reservoir plan for the Xin Chang gas field has been worked out. The results prove that simulation softwarecan work as a powerful tool to design a fracturing reservoir lan for tight low permeable fractured gas reservoirs.

Introduction

Efforts to narrow the gap between investment and output, and to extend production while keeping recovery reasonably stable, encourages the wide use of fracturing reservoir techniques in gas and oil fields to maximize the economic benefits. The key to fracturing a reservoir is forecasting the best well net or post-fracturing production performance, which can provide reliable data for an adjustment plan for gas and oil fields. On the one hand, within tight low permeable fractured gas reservoirs, the fluid has to overcome the minimum pressure gradient to flow, which is characterized by low non-Darcy flow. On the other hand, the gas velocity is very high in hydraulic fracture, which is usually characterized by high non- Darcy flow. This study takes into account both the low non-Darcy flow and the high non-Darcy flow and puts forward an improved fracturing reservoir mathematical model for tight low permeable fractured gas reservoirs.

Fracturing Reservoir Mathematical Model of Tight Clastic Gas Reservoir

Based on successful numerical simulations in fractured reservoirs, and considering the triple medium of matrix, natural fracture, and hydraulic fracture, the fracturing reservoir simulationodel using three-dimensional (3D), two-phase (water and gas) triple medium for tight clastic gas reservoir was developed in which the influence of low non-Darcy velocity and high non-Darcy velocity on fluid flow in tight low permeable fractured gas reservoirs was originally studied at length. The model includes:

Mathematical Model of High Velocity Non-Darcy Flow

Basic Flow Equations

Equation Available In Full Paper....(1)

where

Equation Available In Full Paper....(2)

Coefficient of High Velocity Non-Darcy Flow

Equation Available In Full Paper....(3)

Mathematical Model of Low Velocity Non-Darcy Flow

Equation Available In Full Paper....(4)

General Mathematical Model of Non-Darcy Flow

Equation Available In Full Paper....(5)

when α= 0, β?= 1, the above equation represents linear Darcy flow;

when α= 0, β= 0, the above equation represents high velocity non-Darcy flow; and,

when α?= 1, β= 1, the above equation represents low velocity non-Darcy flow.