This paper documents the application and final results of using surface and downhole tilt mapping to monitor and evaluate downhole drill cuttings disposal at the Joint Industry Mounds Drill Cuttings Injection Field Experiment Project. Knowledge of the created hydraulic fractures was critical for determining the placement of "core-through" wells to evaluate the fracturing disposal mechanisms for both sandstone and shale intervals. Through "real-time" monitoring of the fracture it was possible to detect fracture height growth while the test was being performed and measure that the injected fluids stayed in the intended zone. Surface and downhole tiltmeter diagnostics have been widely used for mapping conventional propped and unpropped hydraulic fractures; however, this is the first application of the combination of surface and downhole tiltmeters to evaluate fracture geometry during drill cuttings disposal.

The application of tilt mapping will significantly aid in the advancement of both non-hazardous (drill cuttings and other oil field waste) and hazardous waste disposal by downhole injection. These applications will include: 1) "real-time" monitoring of the actual created fracture geometry allowing injection to be terminated before the fracture grows out of the intended disposal zone, 2) calibration of existing fracturing models by using the diagnostic results, and 3) aiding in the development of new models, if required, for disposal situations.

The combination of surface and downhole tilt fracture mapping determined the location (azimuth and depth) and geometry (height, length and width) of the hydraulic fractures created by injecting drill cuttings. On-site real-time monitoring (with tiltmeters installed in an observation well close to the injection well) indicated that the fractures did not grow out of the target intervals. These results were confirmed by subsequent "core-through" evaluation wells.

The disposal of waste by downhole injection has proven to be an economically and environmentally attractive solution. The key to moving this method forward is to develop and implement technology that will convince the regulatory community that this is safe, reliable, and permanent. Tiltmeter fracture mapping has played a key role to date, and will continue to, in achieving this goal.

This paper summarizes the results obtained from a comprehensive, joint-industry field experiment designed to improve the understanding of the mechanics and modeling of the processes involved in the downhole injection of drill cuttings. The project was executed in three phases: drilling of an injection well and two observation wells (Phase 1); conducting more than 20 intermittent cuttings-slurry injections into each of two disposal formations while imaging the created fractures with surface and downhole tiltmeters and downhole accelerometers (Phase 2); and verifying the imaged fracture geometry with comprehensive deviated-well (4) coring and logging programs through the hydraulically fractured intervals (Phase 3).

Drill cuttings disposal by downhole injection is an economic and environmentally friendly solution for oil and gas operations under zero-discharge requirements. Disposal injections have been applied in several areas around the world and at significant depths where they will not interfere with surface and subsurface potable water sources. The critical issue associated with this technology is the assurance that the cuttings are permanently and safely isolated in a cost-effective manner.

The paper presents results that show that intermittent injections (allowing the fracture to close between injections) create multiple fractures within a disposal domain of limited extent. The paper also includes the conclusions of the project and an operational approach to promote the creation of a cuttings disposal domain. The approach introduces fundamental changes in the design of disposal injections, which until recently was based upon the design assumption that a large, single storage fracture was created by cuttings injections.

This paper documents the application and results of using surface and downhole tiltmeter diagnostics to map, monitor and evaluate downhole drill cuttings disposal at the Joint Industry Mounds Drill Cuttings Injection Field Experiment Project. Knowledge of the created hydraulic fracture was critical for determining the placement of "core through" wells to evaluate the "disposal domain" or fracturing mechanisms for both sandstone and shale intervals. Through "real-time" monitoring of the fracture geometry (height growth specifically) it was possible to detect fracture height growth while the test was being performed and insure that the injected fluids stayed in the intended zone. Also presented in this paper is a novel approach for using downhole tiltmeters to determine the formation closure stress.

The combination of surface and downhole tiltmeter diagnostics determined the location (azimuth and depth) and geometry (height, length and width) of the hydraulic fractures created by injecting drill cuttings. On site real-time monitoring (with tiltmeters installed in an observation well close to the injection well) indicated that the fractures did not grow beyond the target intervals. These results were confirmed by subsequent "core through" evaluation wells. The use of downhole tiltmeter diagnostics for identifying the fracture closure pressure is also presented. This novel downhole tiltmeter technique aided significantly in determining the initial formation closure pressure or minimum stress.

Surface and downhole tiltmeter diagnostics have been widely used for mapping conventional propped and unpropped hydraulic fractures; however, this is the first application of the combination of surface and downhole tiltmeters for drill cuttings disposal. This is also the first paper to document the use of downhole tiltmeters for identifying fracture closure pressure.

The application of tiltmeter mapping will significantly aid in the advancement of both non-hazardous (drill cuttings and other oil field waste) and hazardous waste disposal by downhole injection. These applications will include: 1) "real-time" monitoring of created fracture geometry allowing injection to be terminated before the fracture grows out of the disposal zone, 2) calibration of existing fracturing models by using the diagnostic results, and 3) aiding in the development of new models, if required, for disposal situations. It was also found that the application of downhole tiltmeter diagnostics is a powerful technique for determining formation closure stress.