Completions and Stimulation Experimental Design, Execution, Analysis & Application for the Permian Delaware Basin Hydraulic Fracture Test Site 2

Abstract

Comprehensive and integrated diagnostics associated with the NETL-GTI Hydraulic Fracture Test Site 2 (HFTS2) in the Permian Delaware Basin enabled a unique opportunity to evaluate stimulation distribution effectiveness (SDE) in the wellbore, near-well and far-field regions (WBR, NWR, FFR) for upper Wolfcamp completions. This paper will summarize the experimental design, execution and analysis for HFTS2 well completions. Results and observations are translated into applications and opportunities for Wolfcamp completions and resource development optimization. A Completions Sub-Committee was created to allow for broad industry input to design the scope of trials to be considered for execution in the HFTS2 wells. Primary objectives were to evaluate Stimulation Distribution Effectiveness (SDE) and test eXtended Stage Lengths (XLS) for stimulation value opportunities. Trials included: 1) HFTS2 operator base-plan completions; 2) more Aggressive Limited Entry (ALE) practices; 3) tapered number of perforations per cluster; and 4) XLS up to ∼ 330’ stage lengths, with ALE practices. Diagnostics included multiple wells with Optic Fiber and Step-Down Tests to evaluate stimulation domain characteristics in the WBR, NWR and FFR regions. The combination of multiple wells with permanent optic fiber installed, and controlled sequencing the stimulation treatment placement operations, enabled good understanding of the frac domains created in the WBR, NWR and FFR. Evaluation of the base-design completions demonstrated good SDE for most applications, from the optic fiber distributed sensing. EXtreme-Limited-Entry (XLE) applications were determined to not be necessary for SDE in the Permian Wolfcamp. Tapered perforation designs were not necessary for good SDE. Risks to SDE were clearly observed with injectivity loss due to mechanical problems with the pumping operations. Risks to SDE were also observed when stage isolation was not effective. Extended Stage Lengths (XLS), up to ∼ 330’ stage lengths with 10 perforation clusters, were generally effective with ALE practices. Acquiring and maintaining injection rate was critical for the higher cluster count stages. The FFR stimulation domain dimensions were generally consistent with the WBR dimension distributions. Significant non-uniformity was observed in the FFR at a cluster dimension resolution. There was good correlation with domain dimensions in the FFR when there was lack of stage isolation the treatment well. Staggered landing depths of the wells, and an instrumented vertical monitor well, enabled assessment of vertical fracture geometry characteristics. Application of integrated diagnostics for completion and stimulation design evaluation enabled assessment of multiple designs in just a few wells. Optic Fiber Distributed Acoustic, Temperature and Cross-Well Strain Sensing (DAS, DTS & DSS), in combination with selective Step-Down Tests, enabled evaluation of stimulation domain characteristics in the WBR, NWR and FFR regions. The results and observations enabled greater confidence for timely completions, stimulations and resource development applications for the Permian Delaware Basin.