Semester of Graduation
Master of Science in Petroleum Engineering (MSPE)
Gas kick migration experiments were performed in a small-scale well prototype model of annular geometry to analyze the behavior of gas kicks in highly non-Newtonian fluids. The objective was to isolate and estimate the effects system compressibility and bubble string out have on the pressure build up in a situation in which a gas kick rises through a noncirculating drilling mud in a vertical well.
The experiments consisted of 2 tests. The first test measured the apparent compressibility of the liquid phase of the experiment – that phase which simulated the drilling mud in a gas kick situation. The second test, performed immediately after the first, was the gas kick test which monitored the pressure rise in a closed-in system in which a gas kick rises through a stagnant liquid phase.
The first test was needed to establish a measure of the compressibility of the liquid phase. Compressibility works to depress the maximum pressure to which a closed system will grow as well as the rate at which the pressure increases. Bubble string out further depresses pressure growth as gas mass is left along the column of liquid. Non-Newtonian rheology increases the likelihood that gas will be entrained by the liquid phase if the liquid exhibits a yield stress.
During the gas kick tests, because the experimental setup was made of steel pipe with no visual confirmation of system dynamics, pressure buildup was monitored at 5 locations – separated by a standard vertical distance for density purposes – throughout the experimental setup. Multiple analyses were made possible by the individual pressure transducers and their relation to each other. Through these analyses, comparisons of the actual bubble rise velocity and the estimate of bubble rise velocity that was made by estimating incompressible liquid phase were able to be compared.
Practical applications of these results include: (1) evidence that the common approach of assuming incompressible liquid phase yields inaccurate results as liquid compressibility increases; (2) a base level of data and evidence needed to establish a link between bubble string out to fluid rheology.
Henry, Nicholas, "String Out and Compressibility Effect on Pressure Rise in a Shut-In Well" (2019). LSU Master's Theses. 4862.