There are many recent efforts on fracture mitigation to ensure competitive infill wells. While operators are trying to overcome asymmetrical fractures caused by existing primary wells, there is also a continuous effort to evaluate the quality of the fracture surface area for the infill wells. SPE 199686-MS covered passive frac mitigation using water to pre-load two Upper and two Lower Wolfcamp primary wells in the Midland Basin. The goal of the study is to determine the success of the pre-load trial by studying the infill well created fractures. We accomplished this using diagnostic plots such as Volume to First Response (VFR), Instantaneous Shut-in Pressure (ISIP), Rate Transient Analysis (RTA) and by characterizing the number of fractures using fracture-type diagnostics. Shear fractures maximize the fracture surface area (FSA) of the well; tensile fractures have limited FSA. Tensile fractures are also a characteristic of asymmetrical fractures, and these, are the types of fractures found in well-to-well communication.
The passive frac mitigation method and initial production results are covered in SPE 199686-MS. The team recorded second by second pressure data with pre-loaded and offset shut-in primary and infill wells. Time was synchronized to absolute reference time to properly assign the origin of fracture driven interactions (FDIs) as they occurred. By use of frac treatment pressure data, the team was able to determine the number of shear and tensile fractures. Then during flowback, the team compared production results per well with the estimated number of resulting shear fractures. For other co-developed infill wells in the same bench, the team also compared the number of shear fractures to determine if frac mitigation technique of preloading aided in maximizing the number of shear fractures.
The team found correlations between the number of tensile fractures measured and location of FDIs. VFR plots confirmed frac-frac connections during the higher-magnitude FDIs. Most interestingly, "low" FDI pressures of 50 -100 psi size were responsible for most of the frac to frac communication. RTA linear flow parameter (LFP), also known as (equation), showed correlation with both VFR and the number of shear fractures.
Incorporating the fracture type in evaluating fracture mitigation techniques provides another dimension to understanding and determining success of the infill well. In our study, frac mitigation using pre-load is not just preventing asymmetrical fractures, but also aiding the maximum FSA created. Production and RTA results confirm that the number of shear fractures and differentiating fracture types are valid metrics. Targeting the right type of fracture during completion when making "on-the-fly" completion modifications may be an important role in frac mitigation.