A New Comprehensive Model for Predicting Liquid Loading in Gas Wells

Abstract

Liquid loading, which can lead to rapid gas-rate decline and can even cease gas production, is a common phenomenon found in most mature gas wells. An accurate prediction of the inception of liquid loading is of great interest to operators, for the reason that remedial measures can be applied in a timely manner to prevent such conditions from being realized, thereby extending the production life of the gas well. However, the mechanism that is responsible for liquid loading still remains controversial. In the literature, at least three different definitions of liquid loading exist. The first definition is based on the intersection of inflow and outflow curves, the second definition is based on the reversal of entrained liquid droplets, and the third definition is based on the reversal of liquid film. These definitions yield different results when predicting the inception of liquid loading. In this paper, a new definition of liquid loading is introduced. This new definition is based on the relative contributions of gravity and residual pressure drop, and it is validated by its agreement with air/water experimental data.A new comprehensive model is developed that is based on the Barnea (1986Barnea ( , 1987 model. For vertical wells, the new model can better predict the inception of liquid loading than the widely used Turner et al. (1969) equation. For deviated wells, it is observed in the field and in laboratories that liquid loading starts much earlier than in vertical wells, and most liquid-loading equations are not appropriate for deviated wells. The new model takes into account the nonuniform film thickness around the circumferential position of the pipe, and, thus, it improves the prediction of liquid loading in deviated wells. The new model is validated through the use of field data in the literature and experimental data obtained at the University of Tulsa. In addition to the literature data, a new set of field data is reported and used to validate the new model, which shows a significant improvement over the droplet model as well as other film models.

Machine Learning Augmented Two-Fluid Model for Segregated Flow

“…That model is based on liquid film reversal of segregated flow and requires pressure gradient and liquid holdup prediction for segregated flow. The critical gas velocity determined from the coupled mechanistic model and the proposed ML algorithm from this study was further evaluated against existing droplet and film reversal models from [25,[66][67][68][69][70][71][72][73][74], as listed in Table 2. It is worth mentioning that the critical gas velocity refers to the minimum gas superficial velocity In addition to liquid holdup and pressure gradient predictions, the new model developed from this study was incorporated into a state-of-art mechanistic model for onset of liquid accumulation prediction proposed in [65].…”

Application of non-uniform film thickness concept in predicting deviated gas wells liquid loading

“…In the oil and gas industry, “critical flow rate evaluation” has been the most widely used and generally accepted approach for predicting the genesis of liquid loading, as critical gas velocity (gas flow rate) is believed to be the major dominating factor that prevents liquid loading in gas wells [[6], [7], [8], [9]]. Fadairo et al [10] observed in their study that, the aforementioned Guo et al model, underestimates the critical flow rate in a gas well, however, they used an iterative method to obtain the critical flow rate.…”

“…According to some experimental studies and field observations, liquid loading begins in deviated wells much earlier than in vertical wells [[17], [18], [19], [20]]. Other researchers have made several attempts to develop models that can aid the calculation of critical gas velocities in gas wells based on two physical theories; the droplet model and film model.…”

A New Approach for Accurate Prediction of Liquid Loading of Directional Gas Wells in Transition Flow or Turbulent Flow

“…While at an identical Reynolds number, as the deviation angle increases, the correction term decreases, and this decreasing trend increases as the pipe deviates, which means that critical gas velocity decreases and liquid-carrying capacity is enhanced. This is because as the deviation angle increases, the gravitational force in the flow direction decreases which will reduce the critical gas velocity [22]. For the convenience of site application, the curve in Figure 3 is transformed into a correction term reference table (see Table 3).…”