Novel Low Expense Cement Slurry Design Based on Enhanced Cenosphere Properties

Abstract

Abstract. In the mature stage of production cycle, depleted zone gives a big challenge in drilling operation especially in cementing part. Some of major risk in the well construction are well control and well integrity, thus loss circulation during cement job and the loss of zonal isolation afterwards is not negotiable. During the peak of oil price, new technology was introduced to have lightweight cement slurry based with the engineered Hollow Glass Sphere (HGS) material. Current fragile of oil price has pushed the needs of low expenses, which part of the major contribution is coming from the well construction. A fit to purpose designed cement slurry with a reasonable cost will be needed to have an economical well to be drilled. HGS material is one of the main contribution in the high cost of well construction, despite the superb feature in having a stable properties of slurry in high pressure environment. Researches has been done by well construction team to reformulate the cement design, in order to have a fit design cement slurry with the unique necessity of Mahakam operation. The main objective is to substitute the HGS material with a conventional cenosphere. However, as the cenosphere is a by-product of coal combustion at power plant, it has wide variation in density and tends to break up in relatively low pressure. Consequently, the risk of loss  circulation during cement job will be severe. A novel study has answered the challenge by applying a reduced cement slurry density at mixing stage of 1.38 SG, in which the Cenosphere will break up during cement placement resulting the cement slurry density when entering annulus is increased to 1.40 SG, hence it will not jeopardize the low fracture gradient of the well as the maximum cement slurry 1.40 SG had shown being tolerable. Additional of other material such as high surface area micro-silica has also helped in lowering the cement slurry density as the second extender. This micro silica is proven to enhance the compressive strength of the cement as well to reduce the waiting on cement time. From four wells which has been drilled and cemented, the approach had shown the expected result, none of the wells has loss circulation and it is recorded until now the sustain casing pressure is nil. The impact of the new design cement slurry on the well expenses has given a 20% of lower cement cost per cement job. This novel cement slurry design has contributing to a new path on the life of Mahakam operation.