Field Study on the Use of Cement Pulsation to Control Gas Migration

Field Study on the Use of Cement Pulsation to Control Gas Migration Dale Dusterhoft; Dale Dusterhoft Trican Well Service Ltd. Search for other works by this author on: This Site Google Scholar Greg Wilson; Greg Wilson Husky Energy Search for other works by this author on: This Site Google Scholar Ken Newman Ken Newman CTES Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Gas Technology Symposium, Calgary, Alberta, Canada, April 2002. Paper Number: SPE-75689-MS https://doi.org/10.2118/75689-MS Published: April 30 2002 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Dusterhoft, Dale, Wilson, Greg, and Ken Newman. "Field Study on the Use of Cement Pulsation to Control Gas Migration." Paper presented at the SPE Gas Technology Symposium, Calgary, Alberta, Canada, April 2002. doi: https://doi.org/10.2118/75689-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Unconventional Resources Conference / Gas Technology Symposium Search Advanced Search AbstractGas flow into cement is a serious problem that results in surface vent leaks and poor zonal isolation in many wells throughout Western Canada. This paper discusses the field testing and application of a new technique called cement pulsation to control this problem. Cement pulsation involves applying short, frequent 700 kPa pulses to the annulus following cement placement. These pulses reduce the gel strength of the slurry, which allows full hydrostatic pressure to be transmitted downhole across the gas zone, thus preventing gas from entering the annulus. This paper also discusses background theory, examines research on the depth to which pulses travel in the annulus, and presents a field study in which pulsation was used to control gas migration in Western Canada.IntroductionGas migration through cement has been an industry problem for a number of years, resulting in poor zonal isolation in some wells and surface vent leaks in others. It is not only a Canadian problem, but a worldwide problem. A 1995 study by Westport Technology revealed that 15% of primary cement jobs in the U.S. fail, costing at that time, $470 million annually.(1) Approximately one-third of those failures were due to gas or fluid migration into the cement.(1) In Canada, we continue to have surface vent flows that cost anywhere from $30,000 to $50,000 to repair. When these vent blows are combined with poorly isolated zones due to gas contamination, the costs become staggering.Gas or fluid flow into cement after it has been placed is caused primarily by the loss of hydrostatic pressure at the gas zone prior to the cement having developed sufficient strength to prevent gas influx. The time period between these two events is called the transition time. Industry efforts over the past several years have centered on reducing the transition time of cements to prevent gas migration. Most research has been focused on increasing the gel strength of the cement, which allows the cement to inhibit gas influx. This has resulted in numerous types of thixotropic cements. Other techniques such as varying the particle sizes of cements(2) have also been evaluated. This particular technique uses low permeability cement to prevent gas from entering the slurry. Although it has been successful, it has not worked universally in all areas.The technique discussed in this paper also examines the effects of reducing the transition time. Rather than focusing on increasing gel strength, however, it investigates delaying the loss of hydrostatic pressure until the cement has developed enough strength to repel the gas.BackgroundSeveral authors have demonstrated that cement starts to lose hydrostatic pressure immediately after pumping stops.(3,4,5,6) This loss is primarily due to particles in the slurry forming an attraction to each other, which creates a fragile gel strength that forms quickly after pumping has stopped. This gel strength allows the cement to support itself, causing a loss of hydrostatic pressure downhole.It has also been established that the attractive forces between the cement particles can be easily broken by vibration or pulsation of the slurry after it becomes static.(1,3,4,7,8,9,10,11) This vibration keeps the cement liquid in the annulus and ensures that it maintains a full hydrostatic head on the formation during setting. In almost all areas of Western Canada, this hydrostatic head is high enough to prevent gas from flowing into the slurry. Keywords: hydrostatic pressure, casing and cementing, pulsation technique, pressure pulse, cement chemistry, strength, spe 75689, husky energy, cement pulsation, vibration Subjects: Casing and Cementing, Safety, Cement formulation (chemistry, properties), Operational safety This content is only available via PDF. 2002. Society of Petroleum Engineers You can access this article if you purchase or spend a download.

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