MATHEMATICAL MODEL OF A ROD INSTALLATION WITH A WELLHEAD PNEUMATIC COMPENSATOR FOR HIGH-VISCOSITY OIL PUMPING

Abstract

Maintaining the profitability of oil fields entering the final stage of development is largely determined by improving oil production techniques and technologies. Currently, due to the growth of hard-to-recover reserves, an urgent task is to develop technical means to improve the efficiency of high-viscosity oil production, in particular, when wells are operated with rod pumping units. One of the most promising ways to solve this problem are pneumatic compensators (РС) - devices that allow to reduce the hydrodynamic friction loads acting on the plunger and rod column by smoothing the pressure and flow rate fluctuations in pumping pipes. Based on numerical modeling, hydrodynamic processes are studied in the pumping pipes of rod installations equipped with wellhead (located on the surface and connected with the switch line) and deep (located in the tubing cavity) pneumatic compensators. A mathematical model of non-stationary fluid flow in pumping pipes and a switch line of a rod installation equipped with pneumatic compensators has been developed. The mechanisms of operation of the wellhead and deep PC are analyzed. It is shown that the PC wellhead allows to significantly smooth out fluctuations in the flow rate at the wellhead during the pumping cycle, thereby reducing the amplitude of pressure fluctuations at the wellhead and in the tubing, hence, the load on the pump plunger and the rod column when the plunger goes up. When working with a deep PC, its working chamber receives liquid when the plunger moves down, which reduces the speed of the liquid in the pumping pipes and the force of hydrodynamic friction of the pumping rods against the liquid. Theoretical dynamograms of the rod installation equipped with pneumatic compensators are constructed. It is shown that due to a combination of effects, characterizing the operation of wellhead and in-depth PC (reducing the load on the plunger when the plunger stroke up to the wellhead of the PC, reducing the hydrodynamic friction force of the rod on the fluid when the plunger stroke down to the deep PC) placement system of pneumocompensators in the pumping pipe and wellhead allows to maximize the efficiency of their work: to increase the minimum and decrease the maximum load on the sucker-rod column and the head balancer to reduce tension in the rods.