Laboratory Development and Field Application of Novel Cement System for Cementing High-Temperature Oil Wells
- Xuxin Wan (SINOPEC) | Hongjun Zhang (ShengLi Oilfield Company) | Yuhai Li (ShengLi Oilfield Company) | Yaxin Yang (ShengLi Oilfield Company) | Huifu Shan (OPT Petroleum E&T Co) | Zhijun Xiao (OPT Corporation Ltd)
- Document ID
- Society of Petroleum Engineers
- Canadian Unconventional Resources and International Petroleum Conference, 19-21 October, Calgary, Alberta, Canada
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 1.11 Drilling Fluids and Materials, 1.6 Drilling Operations, 1.14.3 Cement Formulation (Chemistry, Properties), 2 Well Completion, 1.14 Casing and Cementing, 4.3.1 Hydrates, 2.2.3 Fluid Loss Control, 5.2 Reservoir Fluid Dynamics
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Cementing high temperature exploration wells present a number of challenges to well construction engineers. High bottom hole static temperature (above 100oC), very low pump rates and excessively long job times due to the constraints imposed by tight annular clearances and the use of heavy, viscous drilling muds and cement slurries, and formation complexities (salt layer, high leakoff, unstable formations) all contribute to the operational risks not only during placement of the cement slurry in the wellbore, but also later to the set cement sheath during the life of the well. Various cement systems have been applied with unsuccessful results.
A new cement formulation developed has helped to resolve the problems encountered in cementing these exploration wells and eight jobs have been completed in the field with great success. Synergistic effect between the new retarder and fluid loss control additive improve the system performance significantly such as low fluid loss rate, minimal free water, proper rheology, predictable thickening time, high resistance to salt contaminations, and no adverse effect on set cement strength. An effective laminar flow spacer was also developed and used to displace drilling muds effectively to enhance its placement and improve the cementing bond.
This paper will describe details of thorough and systematic laboratory development of the new cement system and present case histories to document its effectiveness for cementing high temperature exploration wells.
Deep and ultra-deep wells have been drilled in recent years with improvement of drilling technologies and equipment. Cementing mid-to-high temperature exploration oil and gas wells brings chanllemges to well construction engineers . First of all, it is difficult to design cement slurries because most cement additives are not stable at high temperatures. Secomdly, excessively long placement time, low pump rate, and unstable cement slurry properties due to complex well properties such as long interval, tight annular clearance, small hole diameter, heavy and viscous drilling fluids and cement slurries introduce significant operational risks in cementing mid-to-high temperature oil and gas wells. Additionally, salt layer, high leakoff, unstable formations, and production of H2S and CO2 are generally encountered in cementing high temperature oil and gas wells. These formation complexities bring a number of challenges to well construction engineers not only during placement of the cement slurry in the wellbore, but also later to the set cement sheath during the life of the well.
Researchers  reported technical strategies in cementing deep oil and gas wells. The procedures in cementing deep oil and gas wells are basically the same as those for shallower wells. However severe and complex well and formation conditions cause great engineering risks especially in cement slurry design. Proper formulation of dispersants, retarders, fluid loss agents, and other additives becomes critical in cementing high temperature oil and gas wells. Meanwhile, efficient displacement of mud by chemical wash and spacer is also important to enhance cement placement and improve the cementing bond.
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