Solution for a Long - Standing Cementing Challenge - Intelligent Cement Set Control Additive
- Eirik Sorgard (Shell Intl. E&P Co.) | Rodrigo Viali (Schlumberger Pty Ltd)
- Document ID
- Society of Petroleum Engineers
- SPE Offshore Europe Oil and Gas Conference and Exhibition, 4-7 September, Aberdeen, Scotland, U.K.
- Publication Date
- Document Type
- Conference Paper
- 2007. Society of Petroleum Engineers
- 5.2 Reservoir Fluid Dynamics, 1.14 Casing and Cementing, 2.2.3 Fluid Loss Control, 1.10 Drilling Equipment, 5.9.2 Geothermal Resources, 1.6 Drilling Operations, 2 Well Completion, 1.14.3 Cement Formulation (Chemistry, Properties), 4.3.1 Hydrates, 1.6.11 Plugging and Abandonment
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Solution for a Long-Standing Cementing Challenge—Intelligent Cement Set Control Additive
Industry has always found it challenging to cement long zones with a single slurry system. A huge temperature differential exists between the bottom and the top of a long cement column. Cement slurry designed for the circulating temperature at the bottom of the long column will sometimes fail to set at the low temperatures at the top of the cement column. These results in rig nonproductive time and in certain cases can lead to well integrity problems.
While setting unplanned kickoff plugs or plugging and abandoning wells, the bottom hole temperature may not be very well known. The slurry setting is sensitive to temperature, and the setting time can change substantially if the actual bottom hole temperature is different from that used for design. This leads to failure of the cement plugs. This issue is more pronounced around 200°F.
A new generation of engineered cement set control (ECSC) additive has been developed to successfully cement wells in the scenarios mentioned above. The additive works intelligently and not only provides sufficient placement time for bottom of long cement columns where temperature is higher, but at the same time allows for fast compressive strength development even at the top, where temperatures are lower.
A single slurry design incorporating the additive has been used successfully in setting multiple plugs at different depths, with varying bottom hole circulating temperatures, demonstrating the relative insensitivity of the retarder to temperature variation.
This paper discusses successful use of the additive in the field for setting multiple plugs at varying depths and temperatures using the same slurry design. Field cases with results related to the various applications will be provided.
Thickening time of cement slurry plays a vital role in cementing operations. The type of cement, density, fluid loss control, compressive strength and free water are important characteristics as well. However control of cement setting time is essential for successful cementing operations. Several problems can result from ineffective setting time control.
Total operating cost associated with waiting on cement (WOC) is also a critical factor. The time needed to achieve enough compressive strength in order to resume drilling is determined by the cement formulation and the well conditions. A reduction in the WOC time can potentially yield considerable savings to the operator particularly with the high rig daily rates in today's offshore environment.
ECSC additive is almost temperature independent within its temperature range and has a very well defined linear behavior that makes it predictable and safe to use even when small variations in temperature are present. This characteristic allows cement to set more uniformly where temperature geothermal variations are more evident and also when long columns of casing are being cemented. ECSC linear dependency on temperature will prevent longer setting times of cement slurry that may allow oil/gas or water influx in the slurry and compromise good casing isolation. Reduced WOC has being achieved especially in cases where temperature at the TOC is much lower than BHCT.
QHSE (Quality Health Safety and Environmental) Compliance
Today international environmental statutes and guidelines are the strongest driving force to restrict industrial use and discharge of environmentally harmful chemicals. The development of more environmentally acceptable products requires a thorough screening of environmental fitness and status of compliance with relevant laws and regulations. This fact dictates the initiation of several initiatives for environmental improvement addressing human health as well. Results verify that environmentally improved products can be efficient, as well as cost effective.
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