| In the normal course of oilfield production, determine the development well’ productivity is a very important but also very challenging work before officially put it into operation.The accurate assessment and prediction of the single well production is the foundation work in oil and gas field development program. Whether the evaluation about a single well production is accurate or not is directly related to the well network deployment, optimization of the main development technologies, development indicators forecast, ground pipe network construction and a series of technical problems. It is also a key indicator to measure the operability of the oil and gas development program. In general, the capacity is a composite indicator of the dynamic characteristics of the reservoir. It is some kind of dynamic equilibrium achieved in the process of checking each other between the oil and gas reservoir production potential and the various factors. Capacity evaluation and prediction technology is a technology, which can have a comprehensive evaluation to the producing capacity of the oil and gas reservoir. The factors influencing and restricting the production of the single well is uncertain, which can be subjective or objective,So the evaluation to the production of a single well is still an important and difficult task for the exploitation of oil and gas field by far.The yanchang formation of Triassic in Ordos basin is a River～Delta～Lake sedimentary system which is formed under the condition of inland lake basin.It is a kind of hidden lithologic reservoir which has characters of low porosity, low (ultra low) permeability and so on. This papers, which is based on literature research, sums up the results of previous studies and regards the yanchang81formation of Triassic in Ordos Basin as an object, carries out a sedimentary microfacies and reservoir evaluation especially for the Luo1well layer in Jiyuan area, and analyzes the different factors affecting and restricting a single well’s producing evaluation and production from the terms of macro, micro and reservoir fluid as well as human factors. Under the guidance of the theory of fluid mechanics in porous, we have an analysis and optimization about the seepage physical model of complex river delta facies’ oil fields by making full use of lithology, physical properties, electrical properties and a variety of test data. We also have an analysis and evaluation about the single wells’ productivity through dynamic and static data and trial of several wells to research the evaluation and prediction equations of reservoir’s capacity. Finally, we gets a multiple relationship between a single well’s production of oil and gas reservoirs and reservoir thickness, effective porosity, relative permeability, resistivity, starting pressure gradient,pressure sensitivity coefficient and effective hydrocarbon concentration parameters. And on this basis, we deduce a method to evaluate the productivity of a single reservoir well. Through research and analysis, we get the following major findings: (1) We had a systematic analysis about the Chang81reservoir’s microfacies in Jiyuan area by the use of the theory of modern sedimentology and petroleum geology, with the conventional core observation, description, and a variety of analytical laboratory data, which includes thin-section identification, cast thin section analysis, cathodoluminescence, scanning electron microscopy and particle size analysis. The results show that the study area mainly develops the river delta’s sedimentary system of a blanket-type shallow water; delta plain, which is widely distributed, mainly developed distributary channel, distributary channel depressions and natural levee micro-phase; the sandbody mainly develops in the distributary channel microfacies which is the main reservoir; the sandbody’s contiguousness is better, which is a multi-phase river superposition and mostly distributed in a band.(2) Based on sedimentary microfacies analysis, with modern and mature reservoir analysis technology, this paper carries out a detailed analysis and research on the lithology, physical properties, electrical properties and oily capability of the reservoir. In the research area reservoir Chang81, the sand composed mainly of feldspar and quartz, the composition is of low maturity, while the structure is of high maturity; the interstitial material are mainly cement, carbonate cements, argillaceous cement and a small amount of siliceous cement, the content of miscellaneous is less and it’s mainly made of clay material; Sandstone particles are mainly subangular grain and grain-supported; the effect of diagenesis are mainly compaction, cementation and dissolution (mainly the dissolution of feldspar and laumontite) etc. diagenesis stage is middle diagenetic phase A-B.(3) The reservoir space used to reserve sand in the target layer of the study area are mainly the crude residual intergranular pore and feldspar dissolution porosity, radius of pore throat are intergranular small, the average effective porosity is10.51%, the average relative permeability is0.92×10-3um2. overall, reservoirs in Jiyuan area are of low porosity, low permeability and poor property, but the expulsion is of great pressure.(4) The main factors impacting and constrainting the evaluation of the productivity of single well reservoirs at this stage include macro-control factors such as the deposition and diagenesis. Sedimentary microfacies control the intuitive aspects such as distribution, size, thickness of the sandbodies in the reservoir. Diagenesis’ constraints on reservoir are mainly reflected in the change of the effective porosity and relative permeability. Impacts of microscopic characteristics of reservoir on the capacity include reservoir physical parameter, the pore structure (geometry of the pore and throat, size, distribution and its interconnected relationship), the starting pressure gradient and so on. Impacts of fluid reservoir characteristics on the capacity mainly refer to the effective thickness of the reservoir, size and relative permeability form of fluid and subjective factors.(5) According to percolation mechanics theory, combining with the above research results on deposition and reservoir and basing on the statistics of the drilling, logging, well logging, well testing and analysis of laboratory data, we optimizes the relevant set of parameters affecting the productivity to the largest degree(effective thickness of the reservoir, effective porosity, relative permeability, resistivity, thermal solution, the effective concentration of hydrocarbon), which undergoes many practice tests by the way of reliable principle and the gray relational analysis. What’s more, we set multiple relationship between the parameters and the single well production. With the use of Matlab software and multiple linear regressions statistical analysis, we get the evaluation model for the productivity of single well reservoir. Besides, we predict the productivity of some new wells in Luo1oil field in Jiyuan area, the structure shows that the result is good which has certain significance and reference value for the exploration and development of Jiyuan oilfield. |
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