Analysis of Gas-Rise Velocities From Full-Scale Kick Experiments

Abstract

SPE Members Abstract Gas kick experiments in oil- and water-based mud have been studied in a full scale inclined research well. One of the main objectives from these experiments has been the study of gas rise velocities. In order to analyse the gas velocities, the parameters varying during a real drilling operation have been systemized and gathered in a data base. The work represents a significant extension to existing correlations for gas/liquid flows in a full scale inclined annulus with real drilling muds. In high concentration gas kicks the gas rises faster than in low and medium concentration kicks, this is observed for both oil and water based mud. The rise velocity correlations obtained from these experiments is not significantly dependent on gas void fraction, mud density, inclination, mud rheology, and surface tension. The results are quite different from other previously reported correlations, and this has a major implication on kick simulations. Introduction In October 1988, 24 full scale gas kick experiments were performed at Ullrigg in Stavanger by Rogaland Research. The experiments were carried out in a 2020 m long research well with a maximum inclination of 63 degrees. To simulate the gas entry during the gas kicks, Nitrogen and Argon gas was injected through a coiled tubing placed inside the drill string. Data from 19 downhole and surface sensors were collected in order to study the development and control phase of the kicks. In the experiments parameters such as mud type, mud density, gas concentration, mud flow rate, gas injection depth, etc. was varied, and large quantities of data were collected. One of the main objectives from the gas kick experiments was to study the kick process, and how the gas is transported up the well. Data from the downhole and surface sensors, mud and gas properties, flow geometry, and Dow conditions have been systemized in a data base in order to study how these parameters affect the gas rise velocities. A key factor in the development of a gas kick is the rate which free gas rises up the wellbore. Previously published data are mainly limited to experiments performed at laboratory scale, with Newtonian fluids (usually water and air), and pipe geometry's. The practical results of these experiments are limited. Full scale kick experiments with such extensive instrumentation have not been reported elsewhere, and the experiments performed at Ullrigg give the possibility of analysing data gathered under realistic conditions. Comparison between high concentration kicks in water- and oil-based mud, and low and medium concentration kicks in oil-based mud are presented. Two phase flow in vertical and inclined annuli Much of the literature on two-phase flow is experimental and mainly based on flow in small pipes or annuli. P. 331^