Analysis of the Anti-Gas Channeling Effect and Weight Loss Law of Styrene-Acrylic Latex Cement Slurry

During the WOC of cement slurry, gas channeling in the annulus caused by its weight loss is one of the important factors leading to the sustained casing pressure (SCP). Understanding the weight loss modes and law of cement slurry is an important way to prevent gas intrusion in the annulus. Taking the styrene-acrylic latex anti-gas channeling cement slurry system as the research object, the weight loss test of cement slurry was carried out by means of pressure conduction precision measuring device, and the pressure change data of cement slurry under different latex dosage, temperature, gas pressure and simulated wellbore depth were measured, and the anti-gas channeling effect evaluation and weight loss law analysis were carried out. The test found that the styrene-acrylic latex could still effectively prevent gas channeling when the gas-bearing formation pressure (18 kPa) was higher than the bottom pressure of slurry column (12-16 kPa). In this case, the pressure dropped rapidly after this system formed a thixotropic or gelled structure. As the hydration reaction went on, the pressure decreased slowly, then the pressure of cement slurry dropped rapidly again before the thickening, and the dangerous time of gas channeling should appear near the first inflection point. Based on the research results, the anti-gas channeling performance of cement slurry could be evaluated to select the anti-gas channeling cement slurry system suitable for high-pressure gas wells, and such results could provide test basis for the establishment of cement slurry weight loss prediction model.