Video: Effective Zonal Isolation in Horizontal Wells: Mitigating Negative Impact of Mud Channels
- Petr Kolchanov (Schlumberger) | Dominic Perroni (Schlumberger) | Anatoly Medvedev (Schlumberger) | Yan Gao (Schlumberger) | Randy Tercero (Schlumberger) | Larry Todd (Schlumberger) | Bernhard Lungwitz (Schlumberger) | Kenneth Mike Cowan (Occidental Petroleum) | William Turner (Occidental Petroleum)
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- Society of Petroleum Engineers
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- 2018. Copyright is retained by the author. This presentation is distributed by SPE with the permission of the author. Contact the author for permission to use material from this video.
- 7.2.1 Risk, Uncertainty and Risk Assessment, 4.1 Processing Systems and Design, 4.1.2 Separation and Treating, 0.2 Wellbore Design, 2 Well completion, 4 Facilities Design, Construction and Operation, 7.2 Risk Management and Decision-Making, 2.10.3 Zonal Isolation, 2.10 Well Integrity, 2.2 Installation and Completion Operations, 7 Management and Information
- fracturing, horizontal, Mud removal, cementing, channels
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Currently, hydraulic isolation of wells drilled with nonaqueous fluids (NAFs) relies heavily on the elimination of mud from the annuli before the placement of cement. Failure to expel all NAFs will result in residual fluid channels that will compromise well integrity and can even serve as nonproductive communication pathways during subsequent stimulation treatments. To mitigate this risk, an interactive cementing system is presented that is designed to reduce conductivity of the residual mud channels.
Although mud removal remains an integral part of the cementing process, this new cement formulation was developed to improve zonal isolation in the case of poor mud removal. The unique cement system reacts with the hydrocarbons present in NAFs, leading to a reduction of channel permeability and mobility. This significantly improves the likelihood of hydraulic isolation. Specialized testing protocols were developed to enable the demonstration of the capabilities of this new system. In addition, API testing methods and analytical techniques were used to optimize the slurry.
The development of the new cement system focused on the optimization of the active component concentration to give a favorable interaction with NAF, and at the same time, minimize the effect on cement rheology and mechanical properties. Procedures developed in-house demonstrated that the new system effectively reduces hydraulic conductivity of microannuli as well as channels up to several tenths of inches in size. Zonal isolation laboratory experiments were extrapolated to predict whether the modified channels can withstand the range of differential pressures typically seen between neighboring fracturing stages. This is the most critical operation that the cement sheath would be subject to.
Field tests are on-going at the time of writing this manuscript, and the preliminary results will be presented and discussed in this paper.