Designing of Ultralight Slurry for Liner Cementation: Case Study

Abstract

Yaqut -1 well is located in Safed Koh Lease of Dewan Petroleum Pvt Ltd. The well was a Re-entry Well. Original well was drilled in 1984 and was classified as dry well. Dewan Petoleum decided to re-enter the same well and drill down 1356m of 6" hole to test the potential of Chiltan limestone as primary target and Sembar and Lower Goru sands as secondary targets. The Well is located in tectonically stressed/ active area with fractured formations with under-hydrostatic head. This is the cause of severe losses even at Normal Hydrostatic head. The same case happened also with offset well drilled to same depth. Cementation of liner/ casing was very poor which generated many operational issues in post-completion life of the well. Keeping this in mind, we worked on different options of slurry design, mechanical barication i.e use of External Casing Packers, Expandable Rubber Sleeves etc and multistage cementation. The geometry of 6" hole of about 1356m long interval and 5" Liner length of 2278m, did allowed only to manipulate with Slurry weights and discarded all other options. The final option of 7.9ppg Slurry was finalized after authentic Lab test results and ensuring slurry properties. Designed slurry was pumped with only 28bbl loss out of 140bbls. The USIT Log was carried out which showed best cementation results. This paper will discuss in detail the comparison of cementation results of Yaqoot-1 well with offsets. Detailed discussion of slurry designs considered for subject well along with application in under-hydrostatic fractured formations. Lab results of slurry design and USIT Logs have also been discussed in this paper to conclude the strategical justification Ultra Light Slurry Design.