The Mounds Drill Cuttings Experiment: Determining Placement of Drill Cuttings by Hydraulic Fracturing Injection

Abstract

The paper describes a comprehensive field experiment (the Mounds Drill Cuttings Injection Experiment) to improve our understanding of the mechanics and modeling of the processes involved in the injection of drill cuttings. Disposal of drill cuttings from offshore, arctic, and other remote or environmentally sensitive locations is of importance from both economic and environmental perspectives. The transportation of such wastes has the potential for accidental spillage of materials in environmentally sensitive locations such as waterways or wetlands. An attractive disposal option (that is coming into more common use) is to inject the cuttings into deep formations where they will not interfere with surface and sub-surface potable water sources. The major issue associated with this technology is to assure that the cuttings are permanently stored and contained and not transported upward to the surface or toward aquifers. The paper describes the field setting where the experiment is being conducted, the criteria used for formation selection, the technical scope of work, the series of experiments planned and issues which arise when planning and implementing such an experiment. The test program includes the deployment of fracture imaging diagnostic tools to determine the size, shape and orientation of the created hydraulic fractures and the drill cuttings in the fractures. The diagnostic imaging techniques are microseismic mapping, surface tiltmeters, downhole tiltmeters and surface monitoring of injection fluids, pressures and volumes. Observation of cores from the affected area will provide direct evidence of the fractures to support information inferred rom the microseismic data. The plan also includes characterization of the mechanical properties of the cores, and laboratory and numerical modeling of the micromechanics of the cuttings injection process. This experiment is unique in that this is the first time all of these monitoring techniques have been utilized simultaneously at a single location. The paper will add to the industry’s technical knowledge base by providing insight into technical and implementation issues, which arise in planning such a comprehensive experiment. This insight could find applications worldwide for conducting similar field tests.