The Petroleum Accumulation Mechanism And Pool-Forming Model Of Tertiary Igneous Rock Reservoirs In Jiyang Depression

The oil and gas reservoirs of igneous rocks have become important targets of strengthening exploration and increasing reserves in China and it is one kind of subtle oil and gas reservoir in terrestrial faulted basin. On the basis of lots of research results, we use geological and geophysical methods including core observing, core testing, well logging and seismic data to clarify the development and distribution of Tertiary igneous rock in Jiyang depression, to illuminate the characteristics of igneous reserving space, to master the primary factors controlling the development of igneous reserving bedding, and to analyze the forming conditions of oil and gas pools of igneous rock. Moreover, the accumulation mechanism of typical oil and gas pools of igneous rock was deeply studied, the possible reservoir-forming models were proposed and the characteristic of the existed models was given. Main conclusions are as follows:1. The distribution of the oil and gas reservoirs of Tertiary igneous rock in Jiyang depression is decided by the evolution and occurrence of igneous rocks, the hydrocarbon source and the fault zones. It is the upwelling and convection driven by the heat of the matter from the mantle and Tan-Lu Fault Zone that dominate the magma activity in Jiyang depression. The distribution of Tertiary igneous rocks in Jiyang depression is subjected to such four big fault zones as Chengnan fault zone, Chennan fault zone, Yinan fault zone and Shicun fault which is connected to the south boundary. As a whole, three igneous rocks belts formed in Linyi-Binxian, Wudi-Yinan and Jinjia-Caoqiao areas. The origin source of Tertiary volcanic rocks and that of Tertiary intrusive rocks are almost similar and are both from upper mantle. Although the magma in this depression is a mixture of matter of different origins, it isn't mixed by crustal matter. The newer the rock is, the deeper the origin.2. Multi-seismic information and methods including seismic velocities, seismic facies, three seismic instantaneous information, log constraint inversion of deep, shallow later log are used to predict the distributions of the igneous rock reservoir, and good drilling results has been proved .3. Four types of igneous reservoir in this depression were summed up: the basalt reservoir; the diabase reservoir; the volcanoclastic reservoir; the diabase-metamorphic rock reservoir. There are six basic factors controlling the development of igneous pore spaces, including igneous lithological features, igneous rock facies, structural activity, magma cyclicities, lithification and special places of volcano. The six factors play different roles during the development of different type of igneous reserving space, and to every type the most important factors are main factors.4. The ideal igneous rock reservoirs are close to the rich sources of hydrocarbon with good hydrocarbon migration passage, good reserving condition of suitable combination of source-reservoir-cap rocks and excellent traps of hydrocarbon accumulation. And the formation of these igneous rock pools is also decided by the proper matching between the reserving space forming time and hydrocarbon's originating, migrating, accumulating time. The accumulation abundance of hydrocarbon in igneous reservoirs is controlled by the location of igneous rocks in stratigraphics section, the igneous facies, the fault activities, and the type of metamorphic rocks.5. Most of the hydrocarbon source rocks are in the centers of sub-depressions in Jingyang depression, the distribution models of oil and gas reservoirs of igneous rock in this depression can be divided into three types: marginal slope zone, central dome zone and the center of sub-depressions. There are two kinds of migrating passage during the accumulation of oil and gas to the igneous reservoirs in Jiyang depression: firstly, through such migrating passages as sand-body, fault and unconformity the hydrocarbon excluded from the hydrocarbon sources migrated to the marginal fault zone or the central dome zone and went upward to the suitable igneous reservoir and formed oil and gas pool; secondly, the hydrocarbon excluded from the source rocks directly entered the igneous reservoir which intruded into the source rocks and formed oil and gas pools.6. The oil and gas pool-forming models of Tertiary igneous in Jiyang depression are controlled by the igneous lithological features, the igneous reserving space types, the hydrocarbon supply conditions and corresponding hydrocarbon migration and accumulation manner. According to the controlling factors the pool-forming models of igneous rock in Jiyang depression were proposed. They are the other original hydrocarbon volcanoclastic rock pores oil reservoir, the self and other original hydrocarbon basalt rock fissures and dissolution pores oil reservoir, the other original hydrocarbon basalt rock fissures oil reservoir, the self original hydrocarbon intrusive rock fissures and dissolution pores oil reservoir, the other original hydrocarbon structural-lithological intrusive rock fissures oil reservoir, the self original hydrocarbon intrusive-metamorphic rock fissures oil reservoir.7. There is some relationship between the oil and gas reservoir of igneous rock and the reservoir beside the igneous rocks. According to the pool-forming conditions, the pool-forming characters and the distribution of oil reservoirs, three types of combination models were proposed. They are intrusive rocks oil and gas reservoir combination, continental extrusive rocks reservoir combination, and extrusive rocks under water surface reservoir combination.