| Under rapid development of world economy, with gradually increasing of petroleum demand, heavy oil recovery is attracting attention of petroleum experts and scholars at home and abroad day by day. Heavy oil abroad mainly concentrates in some countries and districts such as America, Canada, Venezuela, and former Soviet Union. Heavy oil in our country mainly concentrates in15large and medium oil bearing basin and block, such as Songliao Basin, Bohai Bay, Junggar Basin, Nanxiang Basin and Erlian Basin. Heavy oil has great potentiality to develop. In our country, with severe heterogeneity, geotectonic fault and complex water/oil system, heavy oil reservoir is difficult to develop. Since1960s when heavy oil reservoir begins to be developed, recovery technology of heavy oil reservoir is booming. At present thermal recovery technology of heavy oil concentrates in steam stimulation and steam flooding. Cold production technology such as alkali flooding, polymer flooding, and miscible flooding is also playing a more and more important role in developing heavy oil reservoir. Most technologies are applied in developing heavy oil reservoir and get a good effect.Hong-6block of Hongqian-1wellblock locates in eastern Hongshanzui oilfield, which is in northwest maigins of Junggar Basin. It is20kilometers far away from southwest Karamay. The block faces Zhayier mountain to the north, Karamay oilfield to the east and80block to the south. Being cut by fault, botttom structure form of target Kexia formation is a monocline inclining to southeast. It is piedmont pluvial facies deposition, with interbedded deposition of sandstone and mudstone. Drastic lateral variation and poor continuity characterizes the reservoir. With local concentrated bearing of oil, gross thickness of whole block is considerable and average thickness is about11.75m. Reservoir block is controlled by3major faults and lying three sides high, middle low. Northeast boundary is ke-wu fault, and northwest boundary is west Karamay fault, and southwest boundary is plantain fault. Gross structure framework is a monocline lightly inclining from northwest to southeast. Angle of bedding varies from4°to18°and average angle is8°. Reservoir depth is460～740m and average depth is623m. Reservoir pressure is5.88～8.47MPa and temperature is23.48～29.92℃. Ground oil density is0.9170～0.9512g/cm3and average one is0.9316g/cm3. Ground dead oil viscosity at50℃is186.56～5822.87mPa.s and average one is941.10mPa.s. Average reservoir porosity is19.153%and average permeability is90.320×10-3um2. With mid porosity, mid permeability, low expulsion pressure and good pore connectivity, it is a fair reservoir. As oil area is1.42km2and oil saturation is0.698, IOIP of object block is110.34×104t. The reservoir is almost undeveloped and has great potential to development.Reservoir numerical simulation is comleted by STAR in CMG softwore.On the basis of history matching, according to oil/water distribution of pre-production well after producing for years in numerical simulation, combinating with geologic characteristic, make following development plan and compare them with each other.1. Vertical well patternIn steam stimulation rational well spacing made by reservoir engineering method is about110m-130m. Based on this, use inverted nine spot quadrant pattern of125m well spacing to optimize factors that affecting steam stimulation effect such as steam injection intensity, steam injection rate, and soaking time. Then get optimum steam huff and puff parameters. With above optimum parameters optimize four kinds of well spacings including100m,125m,150m and200m in simulated block. If locate well pattern of Kexia formation individually,125m well spacing should be choosed. If locate a set of well pattern to develop Kexia formation and upper one like Badaowan or Keshang formation at the same time,100m well spacing should be choosed. In later stage of steam huff and puff, cnverting to steam flood is not suitable. With optimum injection/production parameters, forecast development indexes after producing in steam huff and puff producing for8cycles.2. Hybrid horizontal well+vertical well patternHeating radius of horizontal well defined by reservoir engineering method in steam huff and puff is about66m. On basis of this analysis, combinated with actual geology condition of oilfield, simulate producing period in following different well pattern: horizontal well pattern of100m well spacing, horizontal well pattern of150m well spacing, and hybrid pattern located by horizontal well and vertical well of75m well spacing. Hybrid pattern of75m well spacing in which vertical well injecting and horizontal well producing during steam flooding period, is rational well pattern and well spacing in subsequent development plan design. Rational horizontal length calculated by reservoir engineering method is about276m. Then study5kinds of horizontal length as100m,150m,200m,300m and400m.300m is optimized as a rational horizontal length. On basis of above results, get optimum steam stimulation parameters of horizontal well in kexia formation. In optimum plan steam stimulation parameters of vertical well are optimum results of vertical well pattern plan. In later stage of steam huff and puff steam flooding is not suitable. With optimum well pattern, well spacing, horizontal length and injection/production parameters, forecast development indexes after producing in steam huff and puff producing for8cycles.3. Using old well of badaowan formationUse35old wells of badaowan formation to develop kexia formation, and study impact of factors such as steam injection intensity, steam injection rate and soaking time on steam stimulation effect. Then get optimum steam stimulation parameters. Forecast development indexes after producing in steam huff and puff producing for8cycles.In later stage of steam huff and puff steam flooding is not suitable. This plan has best reserve recovery, input/output ratio, and NPV. It is the most economic and effective development plan to develop reservoir of kexia formation. According to study on kexia formation of hongyi-6block, steam flood is not suitable for kexia formation. Major reason is that sand body continuity is poor and injection/production correspondence relation is not ideal. It is supposed to be developed in steam stimulation. If develop kexia formation independently it is supposed to develop it by steam stimulation with old wells in badaowan formation. Optimized injection/production parameters are:soaking time is5days, and steam injection intensity is200m3/m, and steam injection rate is100m3/d. To October in2020forecast development index are as follows:oil/steam ratio is about0.25, and degree of reserve recovery is about25%. If develop kexia and badaowan formation together, following development plan is recommended. Infill wells in badaowan formation and form a close spacing well pattern. Infilling wells first produce in kexia formation by steam stimulation, then returning produce badaowan formation. Convert into steam flooding after producing by steam stimulation for a cycle. Badaowan formation has a deliverability of130000t and Kexia formation has a deliverability of74000t. |
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