Engineered Completion Workflow Increases Reservoir Contact and Production in the Wolfcamp Shale, West Texas
Authors: Ajisafe F. , Pope T. , Azike O. , Reischman R. , Herman D. , Burkhardt C. , Helmreich A. , Phelps M. 
Published: October 2014

In recent years, the number of horizontal wells drilled in the Permian basin of West Texas has increased. The Wolfcamp Shale is a prime target for horizontal well drilling because of its high liquids potential, which makes it an economically viable play. Ensuring maximum reservoir contact and successful hydraulic fracturing can be challenging in the Wolfcamp Shale, which is known for its highly heterogenous nature, high clay content, and high in situ stress.

In the past, Clayton Williams Energy has had limited success stimulating its horizontal wells in the Wolfcamp Shale. These issues can be partially attributed to the highly stressed, laminated and heterogeneous nature of the formation. The conventional geometrically spaced perforation program that is typically selected when log data is not available or is not considered in the engineering design process can result in high pressure differentials between perforation clusters within a stage. The consequence of this includes reduced reservoir contact, incomplete proppant placement, screenouts, and skipped stages in parts of the lateral that are landed in higher stressed rock.

In this study, openhole logging services acquired data through a specialized drill bit. These measurements were then integrated in an engineered staging and perforating workflow. The raw log data was processed to provide both petrophysical and geomechanical rock properties, which were used as inputs to quantify reservoir quality (RQ) and completion quality (CQ) for the engineered completion workflow. The workflow intelligently locates fracture stages and perforations by placing perforation clusters within a given stage in similar stressed rock as opposed to conventional geometric staging, which uniformly spaces out perforation clusters without accounting for the variability in rock properties along the lateral. The workflow honors the desired cluster spacing as much as the stress heterogeneity will allow. This optimization workflow was applied to a number of horizontal wells in the Wolfcamp formation of the Delaware basin in West Texas.

The successful application of log measurements in the lateral for an engineered completion workflow resulted in the first stimulation treatment being placed 100% as designed with no issues. Three wells with log measurements where the engineered completion workflow was implemented showed, on average, a 67% increase in 90 days cumulative barrels of oil equivalent per lateral length compared to three geometric wells in the same area. A 28% increase in designed sand volume was pumped, and the operator also realized a 33% increase in successful stages, where more than 75% of the designed sand volume was pumped. The engineered completion workflow presented below describes a process that is meant to increase the effectiveness of stimulation treatments in horizontal well completions by increasing the percentage of perforation clusters that are stimulated and contributing to production.

A 3D multiwell reservoir model was also designed using well log information from vertical and horizontal wells to delineate the structure of the area and to stochastically propagate the petrophysics and geomechanical properties in the field. Available data included triple-combo logs, more advanced logging suite, and openhole logging data for the horizontal wells. This will be used to establish reservoir and completions quality trends for field development and infill drilling.