Method for predicting scaling trend of CO2 gas-driven wellbore based on stability index

Abstract

The invention provides a method for predicting the scaling trend of a CO2 gas-driven wellbore based on a stability index. The method comprises the following steps that: water sample analysis data arecollected; the concentrations of the CO3 < 2-> and HCO3 <-> under a wellbore condition are calculated by virtue of a trial iteration method according to the temperature and pressure conditions of thewellbore and a known ion concentration through a Ryznar stability index theory; CO3 <2-> and HCO3 <-> concentration curves are drawn when calcium carbonate scales are generated under the temperature and pressure conditions of the wellbore, the concentrations of the CO3 <2-> and HCO3 <-> in wellhead produced water are detected, and corresponding scale removal and prevention measures are taken whenthe concentrations of the CO3 <2-> and HCO3 <-> reach predicted values. The limitation that an existing scaling prediction method cannot predict the scaling trend of a CO2 gas-driven oil and gas wellshaft is eliminated; the method is applied to the prevention and treatment of calcium carbonate scale in an unscaled shaft and can accurately predicte the scaling trend of the CO2 gas-driven oil and gas well shaft, and therefore, a reasonable scale removal and prevention scheme is formulated.

Description

technical field [0001] The invention relates to the technical field of oil and gas field development, in particular to a method for predicting CO based on a stability index. 2 A method for scaling trends in gas drive wellbore. Background technique [0002] In the process of oilfield exploitation, especially in the period of high water-cut oil production, some oil wells will be fouled. Scaling in oil wells will block pipelines and cause production decline, which has become one of the important factors that plague oilfield production. Calcium carbonate scale is a common scale in most blocks. The mechanism of calcium carbonate scaling has been studied in depth at home and abroad. The scaling mechanism is Ca in water. 2+ with CO 3 2- CaCO 3 precipitation. [0003] Calcium Carbonate (CaCO 3 ) scale is a very common scale in oilfield production. Generally, its solubility increases with increasing salinity in water; increasing temperature and decreasing pressure will reduce...

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Problems solved by technology

[0005] However many take CO 2 Oil and gas wells with gas flooding do not have wellbore scaling at the beginning, and subsequent CO 2 During the gas drive development process, due to changes in mining methods and work systems, fouling of wellbore and surface equipment affects production from time to time, and the existing technology does not predict CO 2 Method for scaling trend of wellbore in gas flooding oil and gas wells

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