Significant progress has been made in the last two to three years regarding massive hydraulic fracture treatment design and evaluation. Much of the progress stems from new techniques for analyzing downhole treating pressures and fracture heights. pressures and fracture heights. This paper presents the results of fracture treatment tests on two wells in a tight formation gas play. It gives procedures used for closure stress tests, fluid leakoff tests, and fracture treatment design. It also presents results of MHF treatment analysis to determine fracture length, height, and, in one well, reason for a screenout. The test results on the two wells showed both to have several hundred feet of fracture growth, probably below the perforated zone. This growth, identified by pressure response, was not detectable from post-fracturing temperature surveys. The techniques outlined in this study can be used to reduce treatment screenouts and increase treatment effectiveness in future stimulations.
With the development of tight formation gas plays, massive hydraulic fracturing has become an everyday treatment. In spite of the hundreds of MHF treatments performed in the last five years, there is still mystery regarding what really occurs in the formation during the fracturing process. Significant strides toward understanding the process have been reported by Nolte, Nolte and Smith and Veatch and Crowell. These three papers presented techniques for estimating important presented techniques for estimating important fracture characteristics, such as height growth, width, length, closure stress, and fluid leak-off. Another important fracturing concept, that of critical pressures, was introduced. A fourth paper, by Abou-Sayed, Abmed, and Jones, also presents some of these approaches to fracture treatment design.
These techniques were put to use in a tight formation gas play in southern Wyoming as an effort to increase fracture treatment effectiveness and reduce the rate of treatment screenouts. The thrust of the program was to use downhole pressures recorded during the fracturing treatment to estimate the geometry of the resulting fracture. To accomplish this, gamma ray and temperature profiling were done to estimate fracture height profiling were done to estimate fracture height at the wellbore, 'mini-frac' treatments were used to estimate fluid loss expected in the massive fracture treatment, and step-rate tests and pump-in/flowback tests were run to estimate-the fracture closure pressure. These techniques are explained in more detail in the discussion.
The fluid loss and closure stress data were used to design the massive fracture treatment and monitor the treatment in relation to the computer prediction. Detailed post-treatment analysis was done on each post-treatment analysis was done on each well to give a better understanding of what actually took place during the treatments.
There are several values to be estimated or calculated which are important in fracture treatment design. Although the importance of the values has been understood for years, the estimation of them is still a challenge. The values that were most important in this fracture design work were: fracture height growth, fluid leak-off, and fluid viscosity characteristics.