The integrity of well construction plays an important role to recover the hydrocarbons from subsurface to surface safely and economically. The poor cement integrity behind the casing becomes the cause of gas migration and ultimate well abandonment. The lower Indus basin of Pakistan has the majority of gas producing wells and some of them are plugged due to poor cementing. This is caused by the substantial decrease in the performance of cement slurry with increase in temperature as a function of depth.

Therefore, it is essential to improve the API properties of cement slurry at high temperature for minimizing fluid loss and preventing the gas migration. For this purpose, different types of polymer have widely been used as the additives in cement slurry, but those polymers show thermal thinning behavior above 158 °F temperature. Polymers have also been modified by adding chemicals to improve their thermal stability range. However, the addition of chemicals affects the properties of other additives and increases the cost of cementing operation.

This paper presents the incorporation of Hydroxypropylmethylcellulose (HPMC) cellulose type polymer in cement slurry which acts as a thickener, film foamer and water retention agent. It is capable of increasing the viscosity at elevated temperature. The viscosity of HPMC solutions was determined experimentally at different temperatures ranging from 86 °F to 212 °F with respect to shear rates. The HPMC polymer showed remarkable rheological properties as a thermal thickener at 194 °F. HPMC solution was then combined with cement slurry to evaluate its API properties such as rheology, fluid loss, free water settling, thickening time and transition time at 194 °F. The experimental results showed that HPMC based cement slurries have significant rheology, minimal fluid loss, zero free water, extended thickening time. The transition time of slurries was less than 45 minutes which is considered as the excellent cement slurry for preventing gas migration as per API standards.

It is concluded that HPMC based cement slurries performed as the multifunctional additive, which successfully improved the properties of slurry and prevented the gas migration at high temperature. Hence, field application of HPMC polymer will be a prominent and a cost effective technique for the petroleum industry during cementing operation in the lower Indus basin, Pakistan.

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