| Development of low permeability oil fields for nearly a hundred years of history at home and abroad, early in 1871, the United States discovered and developed the world-famous Grand Bly Telford low permeability sandstone oil (average permeability 7.510.05 × 10-3μm2, the average porosity of 15%). In our country the development of low permeability reservoirs also has a long history, September 10,1907, China’s first oil well drilled on land - Yanchang Oilfield No.1 Well, its production level is world-famous ultra-low permeability layer - Triassic Yanchang oil. From the reports at home and abroad, an basic understanding of geological features and the development characteristics was got toward the low permeability reservoirs:(1)poor reservoir properties, low permeability. As the fine particles, poor sorting, high cement content, generated by the compaction and the role of reservoir rock becomes very dense, permeability is generally less than 100 × 10-3 μm2, minority of which is less than 1.0 × 10-3 μm2;(2)Reservoir porosity is generally low and varies much. Most of which ranged from 7% to 20%, the individual up to 25% (U.S. Barrow Island oil field), Majority of low permeability oilfield has limited effective thickness, so reserve abundance is generally low;(3) High initial water saturation and better crude oil properties. Average water saturation of 30% to 40%,some of which up to 60% (American worthy of Dayton East oil), the majority of oil density is less than 0.85, oil viscosity of less than 3 mPa. S. This determines the reservoirs with low permeability got easily flooding.Ultra-low permeability reservoir is characterized by a significant reservoir permeability is much lower than in high-permeability reservoirs, percolation threshold pressure gradient, some micro-fractures, therefore, ultra-low permeability reservoir stratified water standard has its particularity:(1) ultra-low permeability reservoirs such as tigers Mao Changqing Chang 6 reservoir fracture is developed, a greater impact on waterflooding effect, so the barrier thickness and stability requirements are higher;(2) layer based on a small number of layers within layers segment penetration coefficient of variation coefficient onrush control, heterogeneity worse, fewer small number of layers;(3) ultra-low permeability reservoir permeability special low starting pressure gradient wells generally require fracturing betting, you need to be a higher injection pressure normal water; over the years a strong layer of absorbent try to test a single card single note;(4) the formation of the advantages of low permeability reservoir water channel is currently no effective EOR technology, so deal with water injection to control and prevent the reservoir at a low level of recovery of oil flooded a large area;since the scale development of ultra-low permeability reservoir of Changqing oilfield, as the influence of different water absorption between layers, gradually driving the performance of the low level of water, maintain a low level of formation pressure and production declining such problems. In recent years, in order to improve the poor water absorbing conditions, improve water drive extent that the water evenly distributed vertical stratification, stratified water. Currently the main use of ultra-low permeability reservoirs two dispensing, in order to meet the requirements of fine water, the need to carry out multi- layered water flooding.In this paper, seize the oil-water flow characteristics, based on the injection system for reservoir characterization equivalent, capable of considering the establishment of an inter-compression and shut down wells wells dynamic situation connectivity model. On top of this based on Bayesian theory and the gradient projection method, a model of the overall connectivity constrained optimization method, and provides a new approach to dynamic data analysis and fracture modeling. Innovation and the establishment of a stratified water standards. After the impact of heterogeneity on the basis of waterflood efficiency analysis to determine the stratified injection, integrated use to develop dynamic, dynamic monitoring and numerical simulation methods to establish technical standards for fine reservoir water stratification, namely inter-layer permeability ratio of less than 3 ; barrier thickness ≥1m, provide the basis for the development of fine stratified water injection program.By reservoir engineering analysis and the development of dynamic mathematical statistics, the empirical method and numerical simulation methods are combined to develop a rational formation pressure, bottomhole pressure and water injection intensity, and other fine water policy. Reasonable reservoir formation pressure 12.1MPa; reasonable bottomhole pressure of 6.0-7.5MPa; reasonable injection-productio ratio of 1.1, a reasonable liquid-production rate of 1.7%, predicted the recovery of 12.81% recovery program (simulation ten years), cumulative oil production 26.65. |
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