Best Practices in DFIT Interpretation - Comparative Analysis of 80 DFITs in the Canadian Montney Shale Play

Abstract

Abstract Current practice for conducting minifrac or diagnostic fracture injection tests has been changing with time. The Alberta Energy Regulator (AER) has a pressure and deliverability testing directive that has guidance on those tests. This guidance was updated in late 2021. Many operators from the Canadian Montney shale play submit minifracs to AER, 80 of these minifracs were summarized statistically in this paper. Closure, reservoir pressure, and permeability were the main analyzed parameters in the paper scope. Requirements for pressure and deliverability tests are set out by this newly updated directive. Industry uses minifrac in horizontal wells with multistage fracture treatments when developing unconventional reservoirs. Closure, initial reservoir pressure is commonly being determined with the common well test. Holistic or tangent vs. compliance method are compared for closure pressure in this paper. Readers are eager to replicate results, so for After Closure Analysis (ACA) methods equations that govern the analysis are provided in detail. Published or commercially available holistic and compliance models are compared for closure pressure. Published or commercially available ACA Soliman and Nolte methods are compared for permeability and reservoir pressure. Horizontal wells in 80 unconventional shale field case studies are presented. The fact that the signature of closure pressure is not apparent is a significant finding. Similarity of closure pressure outcomes or estimates for tangent vs compliance is remarkable. Differentiation of reservoir pressure determination for either linear or radial flow are observed. Interpretation on net pressure impact is evaluated and ultimately differentiation on ACA permeability determination is assessed. Analogous shale plays operators in USA and current Canadian Montney Shale play operators will find practical and direct implications. To calculate effective fracture half length and optimize fracture design and well spacing accurate permeability values are needed. To design hydraulic fractures with geomechanics applications accurate closure pressure values are essential. To conduct Rate Transient Analysis (RTA) for resources and reserves assessment in similar unconventional shale plays accurate initial reservoir pressure as an input is fundamental. Comparing analytically closure pressure methods in unconventional shale plays is novel. In addition, practicing engineers or well testing interpreters will find the comparison of different after closure analysis relevant.