THE ANALYSIS AND FORECAST FOR FOULING IN WATER PIPELINES IN DAQING OILFIELD

Abstract

In order to maintain the reservoir pressure and improve oil recovery efficiency, water flood recovery is used commonly in the middle and last periods of oilfleld exploitation. At the same time, in order to avoid environmental pollution, the oilfleld sewage should be reinjected. During that manufacture, variations in the conditions of pressure, temperature and unstability and incompatibility of thermodynamics make scale formation in water flood assize, casing, bottom of the wells, surface equipments and gathering lines. Taking the Daqing oilfield for example, in which the surface gathering lines the scale forming is comparatively serious. In order to improve crude oil processing effect to warm up wet oil, this measure results in scale formation constant in pipelines and equipments, so inner diameter becomes less, leading to back pressure ascent in pipelines, the loss of efficiency of processing equipment, these all have a strong impact on normal activities in oilfield, increase the frequency of maintenance repairs and replacements for pipelines and equipments, and reduce the completion benefit. So forecasting the scaling tendency of surface gathering pipelines, and judging the degree of the scaling tendency or possibility, preventing and controlling scaling effectively is not a negligible research topic in petroleum production technology and oil-gas-water treatment technology. This paper introduces the fouling process, fouling mechanism and the influence factors of the scale, mainly analyses the formation mechanism of calcium carbonate and calcium sulfate, and some factors, such as temperature, pressure, salinity and some thermodynamics conditions. All these factors lead to changes in ionic equilibrium condition, so they will influence the fouling. This paper analyses the main kinds of scale in the gathered transportation water pipeline in the forth plant in the Daqing Oilfield, adopts the method of saturation exponent and energetic solubility to forecast the trend of fouling, reduces the calcium carbonate showing scaling tendency, calcium sulfate having the possibility of scaling. And we will put forward the measures for controlling the scale in pipeline nets in the oilfield. Making use of antiscale is a common measure to control fouling, and this method is convenient and easy to perform, it will work out fouling efficiently in oilfields.