The multistage hydraulic fracturing process is the main stimulation technique to develop tight gas and shale formations. Estimating fracture geometry and stimulated reservoir volume (SRV) is a focal parameter to judge the fracture operation and predict the well performance. RTA and PTA techniques usually assume uniform fracture half-length; however, the fracture length varies from cluster to another due to reservoir properties and stress shadow effect.
This paper presents the performance of single-stage fracture systems with simple bi-wing fractures for all clusters and complex fractures systems which could be close to real fracture network with fixed SRV value. Numerical simulation is used to generate the production and shut-in data from the complex and simple fracture stage models. The production rates and shut-in pressure results from the simulation are then analyzed by RTA and PTA to estimate the stimulated area.
The preliminary results showed that the complex system yields the same or better performance compared to the simple fractures system scenario depending on the formation properties. Generally, the estimated area from RTA and PTA (production surface area PSA) was less than the fracture surface area (FSA) that was used in the numerical simulation. A possible reason for this behavior is the interference between the created fracture on each cluster. As a result, the effective flow area was less than the actual fracture system area. In the case of slightly high permeability formations, the SRV parameter estimated from linear flow analysis in both RTA and PTA was higher in the complex fracture well. Besides, PTA diagnostic plots show a lower estimated skin factor (the difference between the pressure and its derivative curves) in the complex system. While in the case of lower permeability formations, the performance was the same in both scenarios.
This study differentiates between the production surface area and the fracture surface area, and its behavior in complex and simple fracture systems. Therefore, the difference in production performance between wells with different hydraulic fracture systems could be used in understanding the spacing performance.