Currently, a large number of Cenomanian gas storages inWestern Siberiaare at the final stage of development. Gas production from such storage is accompanied by the accumulation of different types of liquid at the bottomhole. One of the methods of solving this problem is the introduction of a foaming agent into the well. To date, there are no computational models that allow us to predict with a high level of accuracy the pressure loss in the tubing of a gas well working with surfactant in the flow. The existing few computational models were created on the basis of bench studies under atmospheric conditions, and the results obtained by them have significant errors. For the study and modelling of gas-liquid flows with surfactant taking into account the influence of pressure, temperature, water-gas ratio and other key parameters, an "Experimental facility to simulate gas-liquid flow and dynamic processes in the tubing of a gas well" was developed and implemented.

Many of the largest Cenomanian gas deposits in Western Siberia are in the final stage of development. There are the liquid loading in the well and gas production decrease. The choice of artificial lift technologies is due to both the technological features of the production process at a particular field, and the economic efficiency of their application. The technology of injection foaming surfactants into the well is widespread in the world, which is characterized by a relatively low level of capital investments and a high level of efficiency, including economic efficiency. There are difficulties associated with the prediction of the pressure gradient under foam flow in a production tubing. This article describes a method for calculating the pressure gradient under foam flow. The results of applying this method for calculating pressure gradient in gas wells of one of the Russian fields on the final stage of development.

Cenomanian gas deposits account for about 80% of natural gas production in Russia. Today, mature Cenomanian gas fields are depleted by more than 75% on average, the reservoir pressure in the productive formation zone has decreased by almost 90% compared to the initial pressure and in some places reaches 1.0-1.5 MPa. Reduction of pressure in the pay zone leads to active intrusion of water from the aquifer. The liquid is loading the well, and gas production decreases. The technology of gas well operation with foaming agent is widespread in the world, which is characterized by a high level of efficiency, including economic. The use of technology leads to a solution to the liquid loading and requires a preliminary selection of the optimal concentration of surfactants. The optimal concentration should ensure the creation of a relatively stable foam and provide a minimum pressure gradient in the production tubing. The article presents the results of studies of CTAB foaming agent influence on the process of liquid removal and pressure gradient in production tubing. Sequential studies to determine CMC, foamability, foam stability, and pressure gradient under foam flow were conducted on small-scale and large-scale facilities. These results can be reliable when using CTAB foaming agent, foaming agents based on it, or other cationic foaming agents in Cenomanian gas wells under the condition of reservoir water inflow. Besides, the effect of pressure on the optimal concentration of the foaming agent was also studied in this work.

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The issue of operation water-cut and "self-kills" wells is one of major aspects in gas production. One of the methods of solving this problem is the introduction of foaming agent into the well. The effectiveness of these technologies requires a theoretical and experimental study of gas-liquid flow with surfactants. We have analyzed existing works and have found out that experimental research in this area was carried out at atmospheric pressure. At the same time, the pressure in the well varies with the length of the wellbore and can affect the properties of foaming agent. The article presents a description of a facility for the study of gas-liquid flows with foaming agents at different pressure values. A method of conducting experiments on the facility, simulating a section of the production tubing of a vertical gas well, has been developed. The relations allowing calculating the volume contents of the phases in the gas-liquid flow with surfactants are proposed.