An electrode-based resistivity tool for fracture diagnostics in steel-cased wellbores

Hydraulic fractures must be contained within the target formation so that they do not contact and potentially contaminate sources of drinking water. To mitigate this risk, research is needed to develop technologies that will advance our ability to diagnose, quantify, and map hydraulic fractures and thus help mitigate the danger that hydraulic fracturing results in the contamination of subsurface potable water reservoirs. Specifically, the challenge is to develop a new technology to more accurately and cost effectively characterize the dimensions, orientation, and proppant distribution of hydraulic fractures in near real time as well as provide long-term monitoring capabilities of these same parameters in cased wells. Currently, induction tools that are placed in the wellbore to make measurements are severely limited in sensing and resolution capabilities. How Problem will be addressed: This research will lead to the development and commercialization of a fracture diagnostics tool capable of measuring the size of propped fractures (with electrically conductive proppant) in cased wells that can be operated during the fracturing operation, or at any time during the well's lifecycle to ensure that underground potable water sources are not contaminated. The basic tool design will also support production monitoring capabilities such as temperature and pressure measurement/logging. Specifically, this project will investigate and develop a modular electrode-based resistivity tool to be used for in-situ measurement of fracture diagnostics in steel-cased wellbores. The tool will be designed to be integrally installed within a production zone casing string and run-in and cemented as part of a multistage cased-borehole fracturing operation. It will use signals generated by locally energizing the casing using sliding sleeves and gap subs. The system will be developed by using novel computational models and methods that will be able to predict the response of fractures to signals generated by locally energized casing. During Phase I, a novel simulator will be developed and preliminary analyses will be performed to investigate the feasibility of the system and to characterize a system design specification. Subsequently, the design parameters will be verified via model based simulations. Additional specifications will be developed during Phase I to ensure mechanical packaging design to be usable as a commercial industrial tool. At the end of Phase I, a system specification will be complete allowing prototype system design and commercialization testing to be accomplished during a Phase II effort. In Phase II, a modular and scalable tool will be prototyped and tested that is capable of operation based on the number of fracture zones required for each deployed application. It is anticipated that the inter-module communications/command infrastructure will be implemented using a mesh network topology, controlled from the surface via a master controller node with multiple downhole modular nodes acting as both router/repeaters and end-devices within the network. It is possible that the physical layer for the network could consist of fiber optic or coaxial cable attached to the casing during make-up and run-in. Also, wireless EM telemetry infrastructure options will be investigated as part of the development of the system specification. At the completion of Phase II development and operational testing of a commercial tool can immediately commence. Key Words: Fracture Diagnostics, Hydraulic Fracturing, Fracking, water contamination, environmental monitoring, potable water, resistivity tool, proppant, induction tool, fracture mapping, conductive proppant, cased well,