| Ultra-low permeability reservoir development get effect from the reservoir properties and fractures in the dual factors,and shows that bad well pattern adaptability,low production rate,low extent of the use of reserves and so on.To solve these problems,starting with the historical evaluation,the paper has found the direction of research.At the same time,we do reservoir research by using seismic,geological and logging synthetical descripsion of reservoir,and use sedimentary time unit subdivision comparative method to research sedimentary characteristics;based on using the productivity equation with starting pressure gradient which Cheng Lu hase deduced for heavy oil reservoir to derive limit well spacing in different forms of well net,we optimize reasonable well net by using the means of numerical simulation.;by comparing productivity equation between drifting stable state horizontal well and common consummate vertical well in the condition of Darcy flow to get formula for calculating the equivalent well diameter to draw the conclusion that horizontal part locates central reservoir is optimal by theory proof and mechanism simulation.We study the characteristics of flow and pressure distribution along the wellbore by solving the coupled flow equation between horizontal pipe flow and three-dimensional seepage flow,then get the pressure loss curve along wellbore through the numerical simulation,and determine reasonable form of perforation finally.Based on theoretical research,the technical and economic limit of the test was further evaluated.It is feasible to take united well net of ultra-low permeability horizontal well implantation and vertical well production to adjust the development through field test.This key conclusion provides a new method for making effective use of this type of reserves.Research and practice showing:(1) Yang Da Cheng Zi oil reservoir has four geologic characteristics in Yushulin Oilfield of Daqing:The reservoir type is the compound lithology reservoir with fault and it's burial depth is deep;Sedimentary characteristics are delta depositional system which are mainly continental distributary fluvial sediment with small scale of sand body;the oil reservoir is mainly ultra-low permeability and low degree of natural fracture;geological reserves are low-abundance. (2) Injection ability of horizontal well is clearly higher than that of vertical well.Water can not be injected into the same perforation formation of the horizontal well in vertical well.At the initial stage,the horizontal well can be injected into 104m3 water per day in the pressure of 20 MPa.But to ultra-low permeability formation,high pressure is needed whether adopting horizontal well water injection or vertical well water injection.(3) Comparing with the vertical injection well,the line of pressure drop is approximately ellipse near the horizontal injection well which is better to form the linear displacement.(4) Formation pressure of periphery oil well rises from 12.28MPa to 17.66MPa after horizontal well injecting water,and production of oil well rises dramatically.However,before horizontal well injecting water those oil wells' oil production was nearly zero.After effective horizontal injection,three oil wells produce averagely 3.4 ton oil per day.At present,the oil production keeps steadily 1.6 ton per day.The development was apparently improved in the test zone.(5) When taking horizontal well water injection,sweep efficiency are significantly higher than vertical well whether oil is produced by vertical well or horizontal well.According to numerical simulation results,the sweep efficiency is between 88%and 92%when taking horizontal well to inject water,yet it is between 67%and 75%when taking vertical well.(6) Through united net research on horizontal and vertical wells,anti-seven horizontal wells injection was thought to be the best well spacing while injector producer distance is less than 129m in the 141 Dong test zone,it is more conductive to improve the efficiency of displacement when horizontal direction paralleling to the direction of crack.(7) Horizontal segment of homogen reservoir should locate in the central part of the reservoir.When injection volume is less than 31 cubic meters per day in the 141 Dong test zone,it is laminar flow in the horizontal segment,and pressure loss is very small just 0.3MPa in the whole horizontal segment.Seeing from fragment absorb water in the horizontal segment,adsorb water volume is low in the center part,with high water-absorbent in both ends.When injection volume is more than 31 cubic meters per day,it is turbulence flow in the horizontal segment,with higher injection volume in the horizontal segment heel and lower injection volume in the horizontal segment toe,but on the whole,the central flow is still low.Therefore,horizontal well perforation should take variable density or non-equidistant to increase central flow in order to form linear displacement to improve effect.We get the same idear about the economic effect that horizontal well better than vertical well. But it is still controversial that which is better make horizontal well as injection water or production.The paper thinks it depends on geology and development condition.,so the horizontal well can be made as injection wells for Yang Da Cheng Zi ultra-low permeable reservoir in the Yushulin oil fields.The reasons are as follows:Firstly it is very difficult for vertical well to inject water.However,horizontal well has the ability of injection.Secondly it can take advantages of section injection and point production.Thirdly it can to exert the overall impact of well group with the horizontal injection wells as the core,and we have seen good technique and economic effect.From development test of horizontal well injection,a set of theoretical methods and technology has been formed,which can guide development of ultra-low permeability reservoirs.It is expected that fifteen horizontal injection wells and forty vertical wells will be distributed in East Block 14 of Yushulin Oilfield of Daqing.The adjustment scheme can be applied in similar blocks such as East Block 12,Shu Block 16 and Shu Block 322.The total area is 37.37km2,and the geological reserves are 25.6081 million ton.For improving the overall development effect of Yushulin Oilfield of Daqing,the scheme will play an important role.Meanwhile,it has great guiding significance for reservoirs with unused reserves in optimum well pattern pattern design and oil reservoir in adjustment of development.
|
PDF Full Text Request