The Combined Technology Of Light Hydrocarbon Recovery By Shallow Cooling-Oil Absorption Development

During the developing of the oil and gas fields, there are a large quantity of accompanying gas. In order to make full use of these accompanying gas, all kinds of devices are used to recover light hydrocarbon in the world . Recovering light hydrocarbon process flow include : condensing separation technology, compressing separation, oil absorption recovery, absorbing method, combined recovery technology. Condensing separation technology is the main method to recover the accompanying gas of oil fields. But this technology consumes much energy and the recovering rate is low. In recent years, there are a lot of new process flow and technology are invented in the world. They are: Refluxing light hydrocarbon, vortex tube (Rangue-Hilsch tube technology, gas wave machine technology, membrane separation technology, SPA technology, DHX technology and Mehra method.The methane content of accompanying gas of Lasaxing oil field is 73.4%?88.1% in Daqing, China. Using 10 sets of shallow cooling facilities with ammonia refrigeration and propane refrigeration to recover C3+ light hydrocarbon components , the refrigeration depth is -20^-35℃, the propane recovering rate is 18.2% 47.1%, and the recovering rate of the C 2+ components is only 52.72%.So, the recovering rate of light hydrocarbon is low. Based on the investigation of the condensation law of the companying gas in Qaqing gas oil field ,the combined technology of light hydrocarbon recovery by shallow cooling-oil absorption is development . This new process flow is based on old shallow cooling process. The process flow reflux light hydrocarbon to absorb propane and butane . The main components of light hydrocarbon are C₅, C₆ and a little C₇+. Light hydrocarbon absorbing the useful components, and the reflux quantity is 8t/h. The process flow utilizes absorbing-resolving-fractionation process to improve the recovering rate of propane and butane . Combined technology of light hydrocarbon recovery gas shallow cool -oil absorption is tested at Sazhong shallow cooling factory of30×04Nm3/d in the field in July, 2002.The testing results indicate the propane covering rate can reach to 61%-85% with combined technology of light hydrocarbon recovery by shallow cooling-oil absorption ,30%-55% higher than that with the recovering technology of ammonia refrigeration and propane refrigeration, and 30%-50% higher for light hydrocarbon recovering rate .Since the combined technology of light hydrocarbon recovery by shallow cooling-oil absorption is tested successfully, it provides a new way for light hydrocarbon recovery of accompanying gas in China . It is particularly suitable for the rehabilitation of light hydrocarbon recovering facilities with propane recovering rate less than 60%, and for process design of new facilities.The key technology the project: The model of the combined technology of light hydrocarbon recovery by shallow cooling-oil absorption is build. The calculation of the phrase equilibrium of the combined technology of light hydrocarbon recovery by shallow cooling-oil absorption. Optimizing the parameter of the temperature ,the reflux quantity etc. of oil absorption process.The innovation of the project: It is the first time in our country to do the experiment on-spot using the combined technology of light hydrocarbon recovery by shallow cooling-oil absorption .And the experiment on-spot is succeeded. From the on-spot data we know, the propane covering rate of this combined process can reach to 68%, 30%⁵5% higher than that with the recovering technology of ammonia refrigeration and propane refrigeration. The products rate is the highest in our country, and that is higher in the world.We use the oil absorption process after ammonia refrigeration, and the reflux quantity is only the third of oil absorption at the normal atmospheric temperature. The resolving process and fractionation take place of the traditional resolving process. So, the energy consumption cuts down. The absorbed rich light hydrocarbon is fractionated into LPG(Liquid Petroleum Gas), the rate of produc...