Research On The Ecological Features And Regulation Of Sulphate-Reducing Bacteria In A CO₂ Flooding Gathering And Transfering Environment

The application of CO₂ flooding technology in Jilin oilfield has obtained a certain progress, however, due to the changes of properties of the production fluid with CO₂ flooding the gathering properties change. A problem occurs when H2 S is produced in gathering and transferring process due to the influence of gathering properties changes, and has affected the normal production of oil field. To preferably apply CO₂ flooding technology and find out the source of H2 S in the CO₂ flooding gathering system, it is necessary to discuss the ecological characteristics of SRB in a CO₂ flooding gathering environment, and carries on the control.In this article, on the basis of analysis on CO₂ flooding gathering ground engineering and the situation of gathering and transferring system in Jilin oil field, and through the test of H2 S content in the associated gas in the process of gathering and transferring and the wellhead H2 S census, we preliminarily draw the conclusion that H2 S is produced by sulfate-reducing bacteria（SRB） from the system. Then we screen out preponderant SRB in the system and investigate its adaptability under the condition of three different growth factors, namely temperature, pH, existence of CO₂. We Obtain its optimal growth temperature is 32℃³7℃, and the optimum pH is 7⁸. Under laboratory conditions the CO₂ can hardly affect the SRB, but in actual gathering system there is promoting of SRB to a certain degree. According to the results of the content change of SRB, the full components of the associated gas, and quality analysis of produced fluid in the process of “the wellhead�'the metering station�'the transfer station�'the joint station�'the water injection station�'water injection well�'the wellhead”, combined with preponderant SRB laboratory adaptive conditions and CO₂ flooding gathering environment, we got the ecological features of SRB in a CO₂ flooding gathering environment and the analysis results indicate the CO₂ flooding gathering system are generally suitable for the growth and metabolism of SRB. Therefore, H2 S is produced because SRB can easily breed in the CO₂ gathering system. Therefore, to solve this problem it needs to regulate and control the activity of SRB in the system, and to heat the water with high temperature for a period before mixed with oil in the pipeline to kill the SRB. The required temperature for mixture water is obtained by using heat exchanger through heat exchange with normal temperature water from joint station. Part of the water is used for mixing with oil, and another part is back to the reheating furnace as recycling water to finally make the heat cycle. At the same time the ultraviolet sterilization device and dosing device can be mounted for joint sterilization. Using single, repeated sterilization method SRB can unavoidably produce adaptability, so in order to control SRB more effectively we need to use a variety of methods alternately or jointly from other aspects.