Volcanic Reservoir Description Based On Stochastic Simulation

With the development of oil exploration at home and abroad, there have been found an increasing number of volcanic reservoir of resources. Back in the late century, Cuba, Japan, Argentina, the United States and the former Soviet Union and other countries, gas and oil have been found in igneous rock reservoir. China from south to north, from east to west of the vast scope of territory, geologists have found igneous rocks as reservoirs of oil and gas reservoirs.Volcanic rocks, as a new special type of reservoir, because of its great depth, complexity and the hidden reservoir to reservoir description and other specialty has been in a stage of qualitative description. The use of advanced algorithms and interpretation of the current theory of its semi-quantitative - quantitative description has become a research hotspot. At home and abroad still no mature theory as a guide.The thesis of the study area for the basin Changling sag, for volcanic reservoir description of this goal, the introduction of stochastic reservoir simulation of the most widely used algorithm for reservoir description of the mature theory to determine the direction of comprehensive multi- research methods. The main research contents include:1. Volcanic lithology identification technology: According to the core description, petrography and casting ordinary thin slice identification and logging lithology in the study area and characteristics of volcanic rock types; to core and slice the results scale logging data, through ECS and conventional logging response characteristics of the lithology, the formation of a fusion cross plot and neural network integrated identification technology volcanic rocks;2. Pore structure analysis: The core descriptions, thin section, CT scanning, pressure mercury on the Combination, from the qualitative to semi-quantitative and quantitative study of the pore throat volcanic type, throat type of pore structure;3. Dual media volcanic reservoir parameters (porosity, permeability, saturation) Well Logging Interpretation: Based on core analysis, ECS calculation and logging measurement data analysis to determine volcanic rock matrix parameters (neutron, density and acoustic lag), using conventional logging data logging interpretation of reservoir parameters, including porosity (effective porosity, fracture porosity and total porosity), permeability (matrix permeability, fracture permeability and the total penetration rate of rock) and saturation (base saturation block, crack saturation and pore saturation). The results of the volcanic core analysis porosity and permeability of reservoir evaluation;4. Stochastic simulation of volcanic reservoir: use of laboratory analysis and interpretation of data logging, combined with geostatistical theory, with the over on the lithology and porosity variability, variation parameter extraction, a true reflection of the study area as far as possible deeper distribution and porosity of volcanic rocks in the spatial distribution of the form of stochastic model, combined with geological analysis and geological knowledge chose the right;5. Volcanic reservoir description: using core analysis, well logging porosity and permeability characteristics and based on the results of the study area heterogeneity of the study and analysis of distribution of reservoir parameters and rules; combination of gas test results, volcanic reservoir classification, classification criteria given in logging, processing of the volcanic section, statistics of reservoir development situation; combination of stochastic simulation to achieve, in-depth analysis of volcanic reservoir distribution, the distribution of facies belts made form.The main technical line is: The core, testing and logging, based on observations by a large number of core, laboratory and theoretical research, the initial formation of a deep volcanic reservoir description technology, including the identification of volcanic rock, volcanic rock double media storage layer parameters (porosity, permeability, saturation) log interpretation techniques, and porosity of volcanic rocks in stochastic simulation, reservoir classification and classification techniques with favorable reservoirs. Of the reservoir characteristics of the integrated application of qualitative description, cross plot analysis, neural network algorithm, sequential indicator simulation, spatial variability analysis methods.Based on the analysis and conclusion volcanic reservoir modeling and reservoir description based on the results of research and put forward some new ideas and innovative approach. Innovations include the following:1. The first time, sequential indicator simulation method is applied to volcanic reservoir stochastic simulation study, and get good simulation results;2. Combining variogram analysis summarized in the study area and porosity of volcanic rocks in the range of variation of the function parameters;3. According to results of sample analysis, log interpretation results and stochastic simulation to achieve favorable volcanic reservoir was first proposed reservoir zonation.Through the above study the following conclusions and understanding of:1. Research group at the top of Yingcheng mainly brown gray, gray tuff, the lower purple gray, dark gray, gray rhyolite. Volcanic component is relatively simple, mainly acidic rhyolitic, dacitic and see a small amount of rough dacitic composition, lithology is relatively complicated, mainly rhyolite, tuff breccia, welded tuff, in situ angle conglomerates and a few sedimentary pyroclastic rocks;2. Study area, type of volcanic reservoir space including pores and cracks in two categories, each subdivided into primary and secondary classes of two subtypes. Of the main volcanic reservoir space porosity and secondary porosity original composition, the main types of pores, pore filling of the residual after the hole, almond body hole, the ball mid-stream pattern grain quality rhyolite glass devitrification produce micro pores, feldspar dissolution pores, pore ash dissolution, carbonate dissolution pores, dissolution of quartz dust holes, gravel between the holes, pellets and tablets around the seam between the shrinkage, cracks and micro cracks. Reservoir pore space based mainly belonging fractured - porous, macroscopically become porous reservoir.3. Volcanic identify basic idea is to "significantly sub-categories, and then gradually broken down," is to use cross plots of log data interpretation routine basis. ECS as a new method of logging of wells in a measure to use. GR-DEN and TH-U plate quickly, clearly and accurately basic distinction in the study area, neutral, and acidic volcanic rocks in the four major categories of acidic volcanic rocks, but the most widely distributed in the study area rhyolite and tuff of the distinction between effects not ideal; use of neutron logging can be acidic igneous lava and acid tuff distinction;4. Core analysis results show that the volcanic rocks of the study area developed cracks and holes, are fractured reservoir. According to mercury curve analysis combined with core porosity and permeability results and findings volcanic reservoir at home and abroad, the study area is divided into five volcanic reservoirClassⅠreservoir pore permeability, porosity, and mean throat radius of the largest saturation value of mercury into the largest and smallest displacement pressure, the best properties, gap degreeФ> 9%, permeability K> 0.1×10-3μm2, for the good of the reservoirClassⅡ: pore structure corresponds to partial pore wide form, with reservoir properties general, smaller displacement pressure, pressure mercury saturation in the higher value, the maximum saturation value of mercury lower; such type of reservoir development in the pore more, including the intergranular pores, intergranular dissolution pores, intragranular pore, dissolution pores, and other types of micro pore over development; pore throat radius of more uniform distribution in the 0.025μm~0.25μm between the porosity distribution range of 4% to 9% and permeability K>0.1×10-3μm2, crack-based reservoir.ClassⅢ: pore structure corresponds to partial pore throat narrow form, with poor reservoir properties, large displacement pressure, pressure mercury saturation in the higher value, the maximum value of the high mercury saturation, pore throat is small, the performance of capillary pressure curve for the skewness characteristics of fine; pore throat radius centered on 0.025μm ~ 0.01μm between a small number of high-value, distribution porosity of 4% to 9% and permeability K <0.1×10-3μm2.ClassⅣ: pore structure corresponds to pore throat narrow form, with poor reservoir properties, large displacement pressure, pressure mercury saturation in the high value of the maximum saturation value of mercury is low, a small pore, capillary pressure curve showed skewness smaller features; such reservoirs, including intergranular pores, intergranular dissolution pores, intragranular pore, dissolution pores, pore type, etc., generally do not classⅡpore structure corresponds to the pore growth, and poor connectivity with some reservoir capacity of the pore structure is poor; mainly distributed in the volcanic breccia, welded tuff, crystal tuff, rhyolite and volcanic breccia Melting; pore throat radius is small, the lack of high value. Very low porosity and permeability and porosity distribution of 3% to 4% and permeability distribution range 0.01×10-3μm2 ~ 0.1×10-3μm2.ClassⅤcategories: less than 3% porosity, a non-reservoir.In the study area to the main reservoir is ClassⅢ;5. Through variogram analysis, the study area are given top business city group of volcanic rocks (mainly developed in the rhyolite and tuff) and different lithology porosity variogram parameters, the results show that the porosity of rhyolite variability slightly higher than the variability of the porosity of tuff; rocks in the range of variation within the range of 80m, nugget = 0.04; acidic lava (rhyolite) and acid pyroclastic rocks (tuff) the porosity of the range of variation in the 30m ~ 50m between the nugget value is between 1 and 2.6. In the study area target layer distribution of volcanic gas reservoirs has obvious characteristics of the gas into the water, according to pilot test the oil reservoir gas conclusions will be divided into gas, bad gas, gas water layers and dry layer four, with properties , electrical, lithology and reservoir characteristics of changes in space as a standard for classification of volcanic reservoir and reserve evaluation, the results of statistics on the study area, the effective thickness of the volcanic gas percentage was 39.4%, and poor gas and gas-water layer effective thickness of the percentage was 13.1%, the percentage of dry layer thickness of 47.5% effective.7. At 5000m depth, the volcanic rock porosity and permeability with depth was not obvious, but the relationship with the location of a larger structure: the volcanic slope in the reservoir structure with larger pores, are in the hole and permeability , local high porosity and high permeability; tectonic uplift belt of volcanic and tectonic depression porosity smaller than the uniform distribution, a low porosity and low permeability reservoir, but the tectonic uplift of the reservoir parameters volcanic tectonic sag slightly better than band; the same tectonic zone, the site of reservoir parameters faults better.