A New Method for Predicting the Position of Gas Influx Based on PRP in Drilling Operations

Abstract

Accurately predicting the position of gas influx not only helps to analyze complex formation structure, but also can provide reference for taking effective measure, such as increasing mud density, increasing back pressure and casing packer, to suppress the gas influx. Predicting the accurate position of gas influx has been one of the urgent difficulties for drilling industry. With full consideration of the important factors such as the virtual mass force, viscous shear force, energy exchange, and narrow resistance, a new method for predicting the position of gas influx has been proposed based on pressure response time calculation. The gas equations of state (EOS), small perturbation theory, and the fourth-order Runge-Kutta method (R-K4) are adopted to solve the model. Also, the pressure response time plate (PRP) which presents the corresponding relationship between position of gas influx and wellhead parameters by several pressure wave response curves calculated by computer programming is given. The results showed that the PRP is unique at different well depth and gas influx rate, and the position of gas influx can be accurately determined by PRP with known wellhead parameters and detected response time. Therefore, without the help of downhole tools, the accurate mathematical method for predicting the position of gas influx is completely feasible.

A Novel Dynamic Model for Predicting Pressure Wave Velocity in Four-Phase Fluid Flowing along the Drilling Annulus

“…Now since obtaining the analytic solution of the aforementioned theoretical model directly is impossible, discretization of the model to a numerical model is required [58]. In this paper, the mathematical methods based on finite difference method provide a numerical solution approach for the dynamic model.…”

Combining Knowledge and a Data Driven Method for Identifying the Gas Kick Type in a Fractured Formation

“…The above studies analyzed the effects of the fracture size and the drilling fluid performance on the gravity displacement through experimental phenomena and measurement data, and proposed the corresponding preventive measures, but did not investigate how to identify gravity displacement after it occurred. By modeling the gas-liquid two-phase flow under a gas kick, the variation characteristics of a gravity displacement gas kick and an underbalanced pressure gas kick, in terms of the bottomhole pressure, free gas, and pit gain, are obtained [11][12][13].…”