| Water drive gas reservoirs are widely distributed in China.Due to the good connection between the water drive gas reservoir and the surrounding waters,when the pressure wave propagates into the waters,the formation water begins to invade the gas reservoir,which leads to the emergence of gas water two-phase flow and the reduction of gas recovery rate.The serious water invasion may lead to the water-flooding in the gas well,resulting in the reduction of development benefit in the whole gas reservoir.At this time,researching on the distribution of residual gas and water control technology on the basis of studying the water invasion characteristics of gas reservoirs is great significant.Based on a large number of water drive gas reservoir related theoretical research,residual gas distribution evaluation method research and water control scheme comparison of water drive gas reservoir,this paper mainly completed the following work:(1)The geological characteristics of TN gas field are analyzed,including sedimentary facies characteristics,physical properties,reservoir temperature and pressure,fluid properties,gas-water distribution and the production situation of the gas field,and the basic overview and current situation of this area are summarized.On this basis,comparing and deducing the calculation methods of single well dynamic reserves,including production statistics method,elastic two-phase method and automatic fitting algorithm based on material balance theory.By comparing the methods,the single well dynamic reserve of layer ?-2 in TN gas field is carried out by using automatic fitting algorithm.The 4 calculation models of water influx are contrasted,including steady state flow model,unsteady flow model,pseudo-steady state model and automatic fitting algorithm,and the advantages and disadvantages and applicability of various methods are evaluated.Based on the automatic fitting algorithm,the calculation of the parameters(water invasion strength,water drive index)reflecting the water activity is completed.The water influx of individual wells in layer ?-2 of TN gas field is calculated by using the calculation results of parameters.The gas saturation of individual wells in layer ?-2 of TN gas field is obtained by curve fitting with empirical formula of phase permeability curve.(2)Based on the study of gas reservoir geological characteristics and reservoir fluid characteristics,a three-dimensional geological model of gas reservoir is established and coarsened to a coarsened three-dimensional geological model.We have done the reserve matching and production history matching work for the numerical simulation model,including gas production and water production fitting of block and single well and bottom hole pressure fitting of single well After successful fitting,production prediction was made,including gas and water production.Based on the fitting results,the pressure distribution,residual reserves distribution and gas saturation distribution of the block are analyzed.The results of gas saturation calculated by gas reservoir engineering method are characterized by interpolation method,and compared with the distribution map of gas saturation simulated by numerical simulation.The distribution of residual gas in this area is defined,and the accuracy of the two methods is further verified.At the same time,the theoretical support is provided for the later design of water control schemes.(3)This paper summarizes the experience of water control in similar gas reservoirs.Based on the previous study of layer ?-2 in TN gas field,a water control method suitable for this area is formulated.The idea of water control is put forward,that is,Strength Drainage on water invasion path and production control and stabilization of other wells.Four gas wells were selected as strength drainage wells,and bottom hole flow pressure and injection volume were designed according to gas lift scale investigation in the gas field site.Combining with the calculation of critical liquid-carrying flow rate,the concrete scheme design of other gas wells is designed.Finally,four alternative schemes are designed,including the scheme of strong drainage combined with production adjustment,the scheme of strong drainage combined with foam drainage,the scheme of medium-scale drainage combined with production adjustment,and the scheme of medium-scale drainage combined with foam drainage.Finally,with the help of numerical simulation technology,the implementation effect of the scheme in the later stage is predicted,and the final optimization is carried out according to the prediction results. |
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