Lateral Wellbore Rock Characterization and Hydraulic Fracture Optimization Utilizing Drilling Cuttings and Mud Log in Cleveland Sand, a Case Study

摘要

Optimizing a hydraulic fracture stimulation in a horizontal well requires an understanding of the petrophysical properties, and the near-wellbore and far-field stresses along the entire lateral. Such reservoir characterization is normally developed from a geomechanical and petrophysical analysis using wireline or logging-while-drilling services that include acoustic and borehole-image logs. Unfortunately, economic considerations often inhibit or preclude complete characterization, especially in the current economic climate. An affordable and convenient alternative for reservoir characterization is to use commonly recorded data, such as drilling mechanics and steering information, to provide a gross characterization. Adding a comprehensive drill cuttings analysis provides insight into rock texture, mineralogy, and rock properties along the entire length of the lateral that is not available from the nominal real-time services. When performed in real time, such studies help ensure that the well stays on-target and within in the pay zone. Such information can later augment the reduced data sets to improve the completion strategy and hydraulic fracture design. This paper describes a case study of a 4-well fracturing campaign in the lower Cleveland sand in Ellis County, Oklahoma. The objective of this project was to compare the completion and production from geometrically stimulated wells against an equal number of wells with an engineered optimization plan. The basic information included drilling data, steering information, and a basic mud and gas log. The optimization on the two engineered wells included an advanced drill cuttings analysis that provided rock texture, mineralogy, and rock properties along the entire length of the lateral. In addition, the drill cuttings were evaluated by a rock laboratory for fluid sensitivity. The results of this study show a significant improvement in the hydraulic fracturing treatment results. The engineered fractured completions were 70% faster— in particular eliminating screenouts that affected operations in one of the geometrically designed wells. The design process is described and has been extended to include the results of the drill cuttings analysis, and incremental results from fracture operations. These are correlated with the plan wells, and a comparison of the available production data is included in the final evaluation of the technique. The lower Cleveland sand was amenable to using this reduced data set for fracture optimization, and this method may be applicable to similar formations.