Well completions are an integral part of providing safe, reliable and continuous access to underground resources such as oil, gas and geothermal resources. Completions are typically considered to be the final step of drilling engineering which includes processes such as setting casing, cementing, and perforating to reach the target formation. Completions provide the conduit from the resource to the surface. Although completions encompass a wide range of disciplines, several key factors ultimately determine the quality of the completion. One of those is cementing and centralizing casing within the wellbore. This white paper examines the current state of the art for centralizers in the context of well completions. The paper will include an introductory primer on well completions to provide the framework for the centralizer discussions. The types of centralizers currently available and how they are used will be discussed in addition to alternative centralizer techniques.

Bottom-hole, above zone monitoring interval, and injection zone pressure data collected during the SECARB project in Cranfield, Mississippi to assess the relationship between pressure field and multiphase field. Submission includes 10-second interval data from Detailed Area of Study wells: CFU31-F1 (injector), CFU31-F2 (observation), CFU31-F3 (observation) and Ella G Lees no. 7 (observation) well located west of the DAS. Associated Publications: Joy, C. A., 2011, The effects of pressure variation and chemical reactions on the elasticity of the lower Tuscaloosa sandstone of the Cranfield Field Mississippi, The University of Texas at Austin, Master’s thesis, 97 p. Kim, S., and Hosseini, S. A., 2013, Above-zone pressure monitoring and geomechanical analysis of a field scale CO2 injection, Cranfield Mississippi, Greenhouse Gases: Science and Technology, doi:10.1002/ghg.1388. Kim, S., and Hosseini, S. A., 2017, Study on the ratio of pore-pressure/stress changes during fluid injection and its implications for CO2 geologic storage: Journal of Petroleum Science and Engineering, v. 149, p. 138-150, doi:10.1016/j.petrol.2016.10.037. Mathias, S. A., Gluyas, J. G., Gonzalez Martinez de Miguel, G. J., and Hosseini, S. A., 2011, Role of partial miscibility on pressure buildup due to constant rate injection of CO2 into closed and open brine aquifers: Water Resources Research, v. 47, W12525, 11 p., doi:10.1029/2011WR011051. Meckel, T. A., Zeidouni, M., Hovorka, S. D., and Hosseini, S.A., 2013, Assessing sensitivity to well leakage from three years of continuous reservoir pressure monitoring during CO2 injection at Cranfield, MS, USA: International Journal of Greenhouse Gas Control, [insert volume no., page numbers], doi:10.1016/j.ijggc.2013.01.019. Nicot, J.-P., Oldenburg, C. M., Bryant, S. L., and Hovorka, S. D., 2009, Pressure perturbations from geologic carbon sequestration: area-of-review boundaries and borehole leakage driving forces, in Energy Procedia (v. 1, no.1), Proceedings of 9th International Conference on Greenhouse Gas Control Technologies, GHGT9, 16–20 November, Washington DC, p. 47–54. Tao, Q., Bryant, S. L., and Meckel, T. A., 2013, Modeling above-zone measurements of pressure and temperature for monitoring CCS sites: International Journal of Greenhouse Gas Control, v. 18, p. 523–530, doi:10.1016/j.ijggc.2012.08.011.

Wellbore cement integrity is paramount to safe, successful oil and natural gas drilling. Cement acts as the primary barrier between the wellbore and the environment. An unstable cement can compromise wellbore control, and research indicates that poor cement integrity is a primary factor contributing to loss of zonal isolation in oil and gas reserves. Although cementing designs and placement practices are well established in many operational environments, the extreme subsurface conditions found in deepwater oil and unconventional natural gas reservoirs pose new challenges to achieving reliable cement jobs. With resource recovery in these types of reservoirs on the rise, the National Energy Technology Laboratory (NETL) and its partners in the NETLRegional University Alliance (NETL-RUA) are examining the performance and integrity of key wellbore barrier materials for which data in extreme environments are limited. One of those materials is wellbore cement. Our researchers are working to understand how various cement mixes perform, with emphasis on potential failure pathways and remediation technologies. This work builds on long-standing research conducted by our organizations to understand and develop technologies for drilling systems associated with onshore oil and natural gas development. It also builds on our work in geologic CO2 storage, which is looking at the effect of stored CO2, acid gas, and brine solutions on the integrity of cements at high pressure and temperature. As the breadth and scope of cementing evolves and industry drills toward deeper, more complex targets, the initial and long-term integrity of cement barriers, and the protocols for placing them, are critical to safe, productive hydrocarbon recovery.