Evaluation Of Gas Well Productivity In LH Water Drive Gas Reservoir

Water drive gas reservoirs are widely distributed at home and abroad,with abundant recoverable reserves and great development potential.However,most of them will engender formation water in the middle and later stages of development,which complicates the development characteristics of the reservoirs.Compared with Conventional gas reservoirs,it is easier to generate a water cone,making formation water breakthrough the bottom of the well and bring the production into the two-phase stage of gas and water,Which will reduce the productivity,increase the pressure of gas-lift in the shaft,and turn out to greatly reduce the recovery of the reservoir.Though,a large amount of research work was conducted in geology,development and production process to improve that.At present,there is still indistinct perception of the permeability model for producing formation interval in the gas-well affected by the formation water.Based on the perforations in the reservoir interval of the water drive gas reservoir,this thesis analyzes the percolation characteristics of different intervals at the bottom of the well,and puts forward a new productivity calculation method and water breakthrough time prediction method for gas wells in water drive gas reservoir.With LH water drive gas reservoir as the research object,after studying on the percolation mechanism of water drive gas reservoir,the thesis has established the physical percolation model at the bottom of gas wells combined with the actual perforation scheme.Furthermore,the author not only considered three types of percolation in the modal,respectively are:non-Darcy radial fluid flow in the interval of perforation,non-Darcy hemisphere-oriented flow and the Darcy radial fluid flow in the interval without perforation,but also deduced a new productivity calculation formula and water breakthrough time prediction formula based on the tree types of percolation.Additionally,the thesis has analyzed the geological and development characteristics of LH water drive gas reservoir,and the influencing factors of productivity,such as the thickness of the gas,the perforation depth,permeability,and the skin coefficient,etc,combined with the actual production data of the gas reservoir.On the other hand,on the basis of the new percolation model,the thesis has established a more comprehensive prediction formula of water breakthrough time and dynamic model of water cone in water drive gas reservoir,which take into account factors such as non-Darcy effect of gas,skin coefficient,original irreducible water saturation and original gas saturation,etc.And the relevant parameters affecting the water breakthrough time of water drive gas reservoir were studied,which is based on the actual production data of LH water drive gas reservoir.The research results present a new approach to predict the productivity and provide solutions to the difficulties in simulating the shape of water cone and predicting the water breakthrough time in water drive gas reservoirs.In short,the thesis gives an effectively guidance for the scientific development of gas wells in water drive gas reservoirs.