Robust Technique for Real-Time Closure Stress Determination

The last five years have seen a rapid expansion in the use of on-site real-time hydraulic fracture treatment analysis. On-site analysis has increased both the power of the supervising engineer and the technical demands placed on that engineer. In order to achieve credible engineering estimates of fracture geometry, fluid efficiency, and potential risks of premature screen-out, the engineer must reliably history-match the observed net fracturing pressure. While the debate will forever rage over the most appropriate modeling procedures for (model) predicting net fracturing pressures; there is little dispute over the urgent need to measure the observed net fracturing pressure. Measurement of net fracturing pressure requires first, and foremost, a reliable estimate of the formation closure stress, to which the net pressure is referred. The literature is replete with methods for measuring formation closure stress. Many techniques are technically compromised by near-wellbore (mechanical) complexities because they attempt to sample a very small rock volume, and others because they measure (elastic) parameters that are only indirectly related to the formation stress. Many techniques are economically compromised because of the costs associated with the required specialized completions and/or tools. This paper documents both the theory and several example field applications of a novelmore » flow-pulse closure stress determination method. The flow-pulse method requires no additional equipment or alterations to the planned wellbore completion. The flow-pulse technique involves pumping a small minifrac (usually with water) and then pumping small pulses (of order 5 barrels) of fluid during the pressure decline.« less