Study On The Technology Of Improving Secondary Oil Recovery Effect

Improving secondary oil recovery effect is the very important issue which is concerned by all the oil producers in the world, is related to the crude output and the productive benefit of maturing field , is the important subdiscipline of oil/gas field development engineering. In this thesis, taking Huatugou Oil field in the West of Qaidam Basin as an Example, synthetically apply theoretical research and practical analysis, stick to systematic thought, lay stress on relevancy, systematicness, comprehensiveness, research the technology of improving secondary oil recovery effect, systematically, built up a method and a study route, which not only provide a good example,but also provide research method reference for similar reservoirs.Based on the former research about reservoir characteristics of Huatugou Oilfield in the West of Qaidam basin, analyze and study on the geologic base attribute of that oilfield ,such as:generalization of oilfield, tectonic feature, reservoir characterization, sedimentary microfacies,reservoir pressure,temperature, reservoir category and drive type of reservoir, property of ground oil ,property of in-place oil ,property of gas, property of local water, stressly study on four problems: the sealing characteristics of fault, the heterogeneity of reservoir, reservoir sensitivity, sedimentary microfacies, which is bound to the improving secondary recovery effect. Use the analytical reservoir simulator ,Eclipse 2005a, simulate the remaining oil of the layer system in huatugou oilfield , select twelve geologic parameters such as: the maximum radius of interconnected pore throat, the mean radius of pore throat,permeability,water-sensitive index and so on, use the gray correlation method, quantitatively evaluate the geologic factors which affect the effect of secondary oil recovery in huatugou oilfield in the west of Qaidam basin, the gray correlation exponent is 0.9804,against"inferior"evaluation criterion. So, the geological condition of this oilfield about the secondary recovery is inferior, generally.Select twelve index marks which can characterize the effect of secondary oil recovery, such as :reserves control level ,the extent of water drive producing reserves, yearly injection-production ratio,the level of producing energy backup, natural depletion ratio, overall depletion ratio, the evaluation coefficient of water-cut escalating rate, the oil recovery rate of remaining recoverable reserves, the state of secondary recovery,synthetical production time ratio of oil/water well,treatment availability, operational cost per ton of crude , build up synergistic evaluation model by using the weighted index method. According to the production datum of huatugou oilfield in the west of Qaimdam basin, find out the score and remark of every evaluation index. By comprehensive evaluation, the secondary recovery effect of this oilfield is"preferable", the synthetical score is 0.4983,vers the"good"score, the difference is 0.050,confirm that there are some latent capacity in improving secondary oil recovery effect in huatugou oilfield .From the influential factors of evaluation indexes of secondary oil recovery effect ,we can conclude that there are four class ,nineteen methods to improving secondary oil recovery effect: the first class is the technological methods which can maintain the normal production of oil/water well, there are eight sorts: pump inspection,sand prevention and washing,corrosion control and inhibition,scale cleanout and prevention, formation break-down, water quality specifications, prevention and cure of casing deformation;the second class is the technological methods which can improve the planimetric effect of secondary oil recovery, there are five sorts: pattern adjustment, set adjustment,fluid diversion ,horizontal well, old well sidetrack drilling; the third class is the technological methods which can improve the vertical effect of secondary oil recovery ,there are three sorts: injection profile adjustment, water plugging, reperforating and formation adjustment;the fourth class is the technological methods which can improve the planimetric and vertical effect of secondary oil recovery at the same time,there are three sorts: fracturing and acidification ,cyclic waterflooding,stratified waterflooding and production. Analyze the adaptability stressly, which these technological methods adapt to huatugou oilfield in the west of Qaimdam basin, come to a conclusion that there are seventeen methods, except pattern adjustment and set adjustment, which can improve the secondary oil recovery effect, according to some mathematical and empirical approach , select layer system and well number, which these technological methods can be brought into operation.Use the analytical hierarchy process(AHP) and Fuzzy analysis to optimize these technological methods for huatugou oilfield in the west of Qaimdam basin ,and then ,use the multistage ARMA model which was created by S.M.Wu to forecast the improving effect, by these mathematical approach ,we can get a conclusion that the score of secondary oil recovery effect should come to 0.5497,which is fallen into the"good"domain in the effect evaluation, if we put these technological methods into operation in huatugou oilfield , so, we fulfill the macroscopic decision making for improving secondary oil recovery effect.