Extending the Life of Mature Field by Light Workover Cementing Technique

Summary Coalbed methane (CBM) is one of the major clean-burning gas resources. Development and usage of CBM can increase the energy supply, improve coal-mine safety, and protect the global environment. The southern Qinshui basin of China is rich in CBM; it is the first area that obtained good results in the commercial development of CBM in China. However, lost circulation is a common problem during cementing through the fractured coal-seams, known as cleats. These cleats form an interconnected fracture network, and this allows cement-slurry loss to the coal-seams during cementing operations. Cleats are often wide enough to accept cement slurry, not just cement-slurry filtrate. Hence, simply reducing slurry density does not ensure a good cement job. Preventing cement-slurry loss to coal-seams while cementing production casing is a major challenge. To solve the lost-circulation problem across coal formations, an innovative hydrophilic-fiber-based spacer fluid and ultralow-density cement slurries with density of 0.95 to 1.20 g/cm3 have been formulated. Laboratory tests have verified the effectiveness of hydrophilic-fiber-based spacer fluid in plugging these cleats of coal seams. The ultralow-density cement slurries exhibit favorable properties. These test results are confirmed by the good field-application results obtained in southern Qinshui basin. Fourteen CBM wells were successfully cemented with the novel spacer fluid and the ultralow-density cement slurries. The combined application of the hydrophilic-fiber-based spacer fluid and the ultralow-density-cement-slurry system is able to successfully resolve the lost-circulation problem in CBM wells, and provides better zonal isolation as well. This paper provides details about the slurry design and field application, and also presents the cement-bond evaluations that verify the conclusions.

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Application of Thru Tubing Technologies in the Caspian Sea Uphole Recompletion

Hadiaman¹,

Mollayev²,

Huseynzade³

et al. 2019

SPE/ICoTA Well Intervention Conference and Exhibition

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Thru-tubing uphole re-completion is a workover technique aiming to re-complete the existing wellbore by temporary abandoning the lower producing zone and subsequently perforate upper layer. There are various techniques used to temporarily abandon the lower zone worldwide. Specific to Caspian Sea development, the temporarily abandonment will only be required to set an isolation plug. However, statistically speaking, success ratio of lower zone temporary abandonment, is quite low using current plugs set in different condition of completion. In addition, the risk of deploying balance cement plug also presents significant challenge due to interval limitation between top of the cement and new perforation interval. It is deemed necessary to find a fit-for purpose solution that provides a solution to the Caspian Sea environment plug and temporary abandonment strategy. A new plug technology, metal to metal system, was introduced to provide assurance isolating the lower zone prior to perforating new upper zone. Subsequently, a wireline deployed or pipe (tubing) conveyed perforation is not an attractive solution to thru-tubing up-hole recompletion technique. A new technology to perforate lively is selected from safety and economic point of view for this specific well. The perforation was done in underbalance condition with intelligent coiled tubing. The uphole re-completion (well delivery) performance was more attractive than other conventional uphole re-completion techniques. This paper will elaborate the success of recompletion techniques by deploying multiple new technologies in the Caspian Sea.

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Extending the Life of Mature Field by Light Workover Cementing Technique

Cited by 3 publications

References 3 publications

Bonding-strengthening technology in coalbed cementing through wettability improvement

Bonding-strengthening technology in coalbed cementing through wettability improvement

The Use of a Novel Spacer and Ultralow-Density Cement System To Control Lost Circulation in Coalbed-Methane Wells

Application of Thru Tubing Technologies in the Caspian Sea Uphole Recompletion

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