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URTeC: 5445 Completion Design Evolution for Saltwater Disposal Injection Wells in the Bakken Play Darren D. Schmidt,* Energy & Environmental Research Center, University of North Dakota; Jeffrey W. Bader, Ashleigh Day, and Mark Bohrer, North Dakota Department of Mineral Resources Copyright 2021, Unconventional Resources Technology Conference (URTeC) DOI 10.15530/urtec-2021-5445 This paper was prepared for presentation at the Unconventional Resources Technology Conference held in Houston, Texas, USA, 2628 July 2021. The URTeC Technical Program Committee accepted this presentation on the basis of information contained in an abstract submitted by the author(s). The contents of this paper have not been reviewed by URTeC and URTeC does not warrant the accuracy, reliability, or timeliness of any information herein. All information is the responsibility of and is subject to corrections by the author(s). Any person or entity that relies on any information obtained from this paper does so at their own risk. The information herein does not necessarily reflect any position of URTeC. Any reproduction, distribution, or storage of any part of this paper by anyone other than the author without the written consent of URTeC is prohibited. Abstract Disposal of produced water is a critical component of unconventional oil development. The significant increase in Bakken production over the past decade in concert with the expansion of saltwater disposal wells geographically, places new demands on the storage reservoir. Development has spurred investigations of the reservoir and well performance. Specific to the Williston Basin and Bakken play, new disposal wells do not always meet injectivity expectations, and some operating wells decrease in performance over time. Operators have responded with well interventions and new well completion techniques. Well data collected from the North Dakota Department of Mineral Resources are used to provide an analysis. Baseline well performance, well testing, and a review of the developments in recent well completions are discussed. Analysis compares calculated performance to field data and highlights the potential for improved injectivity. Introduction The North Dakota Department of Mineral Resources (ND DMR) regulates the disposal of produced water from oil and gas wells through the Underground Injection Control (UIC) Program established by the Safe Drinking Water Act to protect underground sources of drinking water. The UIC Program is overseen by the U.S. Environmental Protection Agency (EPA). ND DMR has regulatory primacy over Class II and Class III injection wells in North Dakota. Class II wells are either designed for disposal of oilfield fluids or as injection wells for enhanced oil recovery. Class III wells are for subsurface mineral mining, of which none are currently operating in the state. ND DMR regulates the permitting, construction, operation, and closure of injection wells. Downloaded from http:/onepetro.org/URTECONF/proceedings-pdf/21URTC/3-21URTC/D031S075R003/2477833/urtec-2021-5445-ms.pdf by Yangtze University user on 14 February 2022URTeC 5445 2 Permitting and well construction regulations are structured to protect groundwater sources. A typical well construction diagram for a saltwater disposal (SWD) well is provided in Figure 1. Some of the various permitting, construction, and operating requirements include the following: Public hearing and notice. Notification to surface owners within mile. Geotechnical analysis of shallow aquifers. Geologic requirement for the target formation to have upper and lower confining zones to prevent migration of fluids into other formations. Casing and cement requirement to protect and isolate all formations, protect pipe through salt sections, and isolate the uppermost sand of the Dakota Group. Review of geology, injection pressure, well construction, neighboring wells, sampling from freshwater wells, and analysis of the injected fluid. Tubing is required, and the tubing packer must be set at an approved depth. The operator must demonstrate mechanical integrity. The operator must demonstrate adequate cement. The operator must submit monthly reports with injected volumes and stabilized surface injection pressure. The operator must report first injection date. The operator must monitor tubing and casing pressure. Remedial work must be reported. Geology The Inyan Kara Formation is of specific importance as it consists of thick sandstone bodies deposited in incised valleys present along the coastline of the Cretaceous Western Interior Seaway. These valleys were incised by north-northwesterly flowing rivers that drained into the seaway from highlands to the east-southeast. The valleys formed at sea level in the Cretaceous seaway dropped in North Dakota twice over a period of approximately 10 million years. Sea level eventually rose again, and the valleys were flooded, forming estuaries where very clean reservoir sands were deposited, again in two

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