ABSTRACT

Based on the colloidal stability theory, the hydrophobic associating powder anti-dispersant (HAPA) for high water cut oil and gas well cementing was developed to solve the problems of water intrusion in high water-bearing formations. Compared with conventional cement slurry, the anti-dispersion performance of the underwater non-dispersion cement slurry with HAPA are significantly improved, which is manifested by cement loss is below 4g, pH value = 7, and the underwater/in-air strength ratio is ≥74%. As an effective tool to improve the cementing quality of water-bearing formations, the underwater non-dispersion cement slurry had been applied in 30 wells. It can solve the problems of multiple water layers, small spacing between oil layer and water layer, and active bottom water. With the high-quality rate of cementing improved by over 10% on average, the technology effectively improved the cementing quality and ensured the sealing integrity of cement sheath.

INTRODUCTION

With the deepening of the oilfield development process, most of the old oilfields around the world have entered a period of high water cut or ultra-high water cut (Yuan, 2018). Maling oilfield BS district of Changqing old oilfield in China is in the middle and later field life, with high water cut of 90.8%, high and low recovery percent of 26.1% and 0.25%, respectively (Shangguan, 2015). The Tuo-21 Fault Block of the Shengtuo Oilfield in Bohai Bay Basin has entered the stage of ultra-high water cut of 97.2% (Yu, 2022). In the Shengli Oilfield, which is the second-largest oilfield in China, the average water cut has reached more than 95% (Bai, 2022). The Daqing Oilfield has entered the late stage of high water cut period with water cut of the oilfield is 88.9% (Pei, 2006). Ugra, the leader of Russia's oil production, has achieved a moisture water cut of 90–95% at the main deposit since 2009 (Bulatov, 2020). Within the United States (U.S.) alone, the oil and gas industry generates 15 billion to 20 billion barrels of produced water annually (Kassab, 2021). As the last process of drilling engineering, cementing is a systematic, important, one-time and high-precision engineering operation, which is directly related to the protection of oil and gas resources and the productive life of oil and gas wells. When conventional cement slurry is used for cementing in formations with high water cut, it is susceptible to erosion and dilution by formation water in the process of waiting on cement. A large amount of water in formations with high water cut of oil and gas well will have a direct impact on cementing operations (Al-Khayyat, 2022). Strata water or injected water will change the hydration and solidification process of cement slurry, which in turn affects the mechanical properties of cement stone. Moreover, water invades and destroys the cemented structure of the second interface of cementing, affecting the cemented strength of the second interface, leading to annular channeling, and reducing the service life of oil and gas wells. In more serious cases, it will lead to the complete failure of the hydraulic sealing integrity.

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