Scale management of production wells via inhibitor application in supporting injection wells

At the present time, the YUKOS Oil Company is applying various techniques to maximize oil recovery. Some of these techniques, such as waterflooding, are leading to an increase in the number of wells that face scaling problems. Various technologies are being used for scale management in these wells, including, for example, continuous inhibitor dosing utilising surface dosing systems. This method has some disadvantages, including the high cost of the service. In addition, this technology only protects downhole equipment from damage by scale deposits, but the bottomhole formation zone remains unprotected. Some years ago we recommended that production wells be protected via scale inhibitor application in the injection waters used for reservoir pressure control and sweep. Experiments conducted have shown that this technique may be used for certain production well types with scaling problems when these are located in relatively close proximity to their supporting injection wells. This paper presents the experimental and field results when this technique was tested in the South-Surgut oilfield. Before testing, a preliminary investigation of the formation geology and hydrodynamic connectivity between injection and production wells was carried out. Next, a large number of experiments were carried out to select an efficient inhibitor chemistry, to test for inhibitor adsorption on the reservoir rock, to evaluate an initial MIC for the solution, and to determine the inhibitor dosing periodicity. During testing of this technique, the inhibitor concentration in the produced water was regularly measured, and the impact on protection against scale was continuously evaluated. It was demonstrated that the inhibitor concentration in the produced water did not decrease below 5-10 ppm on average during 150-200 days for all wells. As a result, the interval between workovers for pump equipment increased by approximately 2.5 times. Furthermore, oil production was increased relative to the period before introduction of this technology. An economic evaluation was carried out that showed the viability of using this technology for the protection of wells in a compact injector-producer pattern.