Enhanced Gas Recovery Using Improved Flow-back in Multi-stage Fracture Treatment in a Vertical Well in a Tight Gas Reservoir
TRAN, H.D. and TRAN QUANG H.
Engineering Honours 2014
Australian School of Petroleum
University of Adelaide
Tight gas reservoirs are considered as very low permeability reservoirs which cannot be produced at an economic rate without advanced stimulation technologies. Hydraulic fracturing is one of the best methods to stimulate a tight gas well. Most fracture treatments result in 3-6 fold increases in the productivity index. The success of conductive fracture depends on the hydraulic fracturing design, planning and execution in the target formation. However, hydraulic fracturing would not be successful if fracturing fluids are not returned back to the surface. In this study, we have investigated the problems limiting fracturing fluid clean-up in the Patchawarra Formation and developed a better understanding of the issues which lead to ways to improve clean-up.
In this research, input data from thirteen wells in Cowralli field was analysed for data availability and quality. A single well was selected for simulation which had available standard logs as well as mini-frac analysis of all the reservoir sands. Two different commercial software were integrated to construct the 3D hydraulic fracturing model (GOHFER) and reservoir simulation (ECLIPSE). The 3D hydraulic fracturing model has been constructed first using GOHFER. The output from GOHFER was then imported into a 3-D, two-phase flow reservoir simulator (ECLIPSE) and was used to quantify the clean-up fluid process as well as predict future performance of the reservoir. The sensitivity analyses were then conducted using different fracturing fluids and reservoir properties in order to determine the factors affecting clean-up.
The results showed that the cross-linked fluid delivered a good performance in tight gas formation in terms of fracture length, proppant placement, fracture conductivity, and fracture efficiency. The cross-linked fracturing fluids used in the sensitivity analyses were the delayed borate-cross-linked fluid. Although other fluids perform slightly better on propped fracture length, it is not enough to make up for clearly superior performance by the delayed borate-cross-linked fluid on proppant placement, fracture efficiency, and fracture conductivity. In terms of reservoir simulation, results showed that high drawdown, high matrix and fracture permeability, short shut-in time and low capillary pressure will lead to a better fracturing fluid recovery.