Motion Law Of Waterflood Front In Low Permeability Reservoir

In this paper, we study on the Changqing low permeability oilfield which has the characteristics of strong heterogeneity and fracturing. Combined with physical simulation experiment, numerical simulation and reservoir engineering methods, motion law of waterflood front was studied. The main research results are as follows:(1) Waterflood front calculation for low permeability was established which take the two-phase starting pressure gradient and heterogeneity into considered. From the method, distribution of waterflood front and water breakthrough time of wells can be calculated. Results show that because of the high heterogeneity, it’ll have a huge impact on waterflood front. The difference in permeability causes uniform distribution of water flooding energy in well group, so that speed of waterflood front is very different. Compared with the traditional method, the new method has great advantages.(2) Influence of well array distance and fracture penetration ratio for waterflood front was analyzed and the timing of fracture impact on waterflood front was calculated. Finally, well spacing of inverted-nine well pattern was optimized. The calculation show that as the permeability promoted, the penetration ratio increased, the timing of waterflood front affected by was significantly ahead. Experiment and numerical simulation proved that for the model of a single crack, when the well spacing is 400* 100m and with the permeability of 0.2mD, the best penetration ratio is 0.7. For the inverted-nine well pattern, when the penetration ratio is 0.7 and with the permeability of 0.2mD, the best well spacing is 400* 100m.(3) Through experiment and numerical simulation, the existing calculation formula was amended. Calculation method of sweep efficiency after the plane adjustment in low permeability reservoir was established. Results show that in the low water period, five spot and nine spot well patterns have the similar sweep efficiency and in the process of development, the nine spot well patterns has significant advantages. After adjustment measures, well spacing density increases and the sweep efficiency greatly improved.(4) Simulation system for large scale physical model of low permeability reservoir was established. Through analysis of the conventional mercury injection, choose the natural outcrop with similar target block pore structure characteristics. Study on the actual movement rule of water flooding in well group, and the degree of recovery of each district are analyzed, and puts forward the corresponding suggestions for tapping the potential of remaining oil and development adjustment scheme.(5) Influences in development indexes of different well pattern infiling adjustment time were analyzed. Results show that after the pattern infilling adjustment, the average recovery rate is increasing by about 5.38%. Infill drilling of well pattern adjustment will enable more reservoir area affected by water flooding, so that the development of relatively poor oil sand is improved.But late encryption adjustment will result in the loss of recovery, but the effect on water storage rate to water consumption rate is not obvious.