At present, the purpose of natural gas exploration in China is no longer to find the medium-large gas fields, but large gas fields. Enhancing the quantitative or semi-quantitative studies on the main factors of controlling the formation of the large gas fields, especially defining the area with gas generating strength more than 20×108 m3/km2 is an important method of finding large gas fields. The fact that coal generates more gas and less oil is the basic rule. The study on natural gas resource studies in China should change form geological resource evaluation to recoverable resource prediction. China has a recoverable resource of natural gas 11.44×1012 m3 to 13.32×1012m3. The natural gas exploration has much potential. Strengthening the study on high potential gas-rich area is significant for Chinese natural gas industry. The natural gas geochemistry study should combine with the natural gas geology.
The strategy, principle and pattern of gas development are controlled by reserve, gas properties and gas reservoir type. According to those, this paper carries on a detailed research and put forward corresponding measures. The conventional gas reserve is limited in China. So, we should work for enlarging gas reserve and strengthening effective exploration and development of unconventional gas. On the other hand, the gas import should be taken into consideration. Only if insisting on integrated development work, and applying relevant technologies in terms of the development properties of different gas reservoir types, we can just inc rease profit and decrease costing.
Natural gas geochemistry study has become an important basic work in the exploitation of natural gas. Because of the mixing of gas sources and the multiformity in the natural gases chemical composition and isotopic composition, the forming process of gas pool is very complex. It is important that take accurate geochemistry analysis data in natural gas geochemistry study. Natural gases formed by different types and different evolvement stage of source rocks have different chemical composition and isotopic characteristics. According to these, we can confirm the forming type of natural gases. After these, using the relation between natural gas carbon isotope and Ro, we can make sure the maturity ofnatural gas. There are many reasons making the variety of the carbon isotope series. Being an assistant index to judge the natural gas resource, noble gas can distinguish whether natural gas mixed by deep gas or not. When it is made sure that the natural gas has been mixed by deep gas, the 40Ar/36Ar value is used to estimate the age of source rock. When applying these geochemistry indexes to explain the forming characteristics of natural gases, we must combine the geological background.
The present paper briefly introduces the traditional theory on hydrocarbon geneses and the concept of "commercial deadline of exploration", outlining that the study on deep oil and gas is to break through "the theory on the hydrocarbon generation from late kerogen" and to search for deep oil and gas resources beneath the current explorative depth. Moreover, the theory on deep oil and gas as well as its key effective factors is also discussed in detail. The study on the abiogenic gas concerns searching for natural gas resources generated from abiogenic (inorganic) processes in the deep earth, the paper discusses in detail the theory on the abiogenic gas, introduces achievements obtained in this research field and reports the discovery of abiogenic gas reservoirs from the Songliao Basin and their evidence, providing a typical research example in this research field. In addition, on the basis of the above researches, a kinetic-thermodynamic model on the organic matter evolution in the interior earth.
The hydrocarbon resource of Tarim Basin is abundant. By the end of 2002, Tarim Oilfield Company, PetroChina Company Limited, has found cumulatively proved OGIP 646.433 BCM, with recoverable reserve 444.397 BCM. It can produce 12 BCM natural gas per year for 30 years steadily for WEP project. As the proved reserve is only 7.7 percent in potential resource, the exploration prospect is bright. It is predicted that the natural gas exploration will step into another increasing peak soon. In 2015, the proved OGIP will reach 1.3 to 1.5 TCM, and production of natural gas will reach 30 BCM a year. By the time, the Tarim Basin will become the biggest onshore natural gas production area in China. After decades of exploration and development, Tarim Oilfield Company has accumulated much experience and mastered series of techniques. These are the bases to achieve the task of WEP project.
Carbonate source rock research is one of the important problem in petroleum organic geochemistry and in petroleum exploration in carbonate rocks. One of the argument is the evaluation standard of source rock, and the focus is minimum value of TOC of source rocks. Aimed at gas fields of Permian and Triassic carbonate of southwest Sichuan basin, combining gas reservoir geochemistry with petroleum geology, utilizing advanced geochemical analysis, correlating gas with source rock, observing the variation of TOC in vertical section, the article has deduced the minimum value of TOC of source rock in theory. And conversely, based on the geological condition and the background of exploration, calculated the hydrocarbon
source quantity, compared with the prospective resources, the author determined 0.3% as the minimum value of TOC of carbonate source rocks in Permian carbonate of southwest Sichuan basin. By the way, the differences of mechanism, conditions, influence and process of hydrocarbon formation between the carbonate and clastic rocks is discussed.
Natural gas whose heavy hydrocarbon components are with abnormal heavy carbon isotope was obtained when drilling both Ordovician buried hill and deep beds in Banqiao Sag The analysis of light hydrocarbon group composition, C7 light hydrocarbon composition, naphthene index, benzene and toluene carbon isotope proved that the gas mainly sourced from the Lower Tertiary kerogen Ⅱ2 source rocks Moreover, the author further denied the possibility of coal|formed gas to be the hydrocarbon source on the basis of Carboniferous and Permian distribution and the secondary hydrocarbon generation condition. Applying the δ13C2 and δ13C2-1 correlation chart analysis, the author finds out that the nature gas with abnormal heavy carbon isotope in Banqiao Sag can be classified into three types, i e. humic gas in early and medium mature stage, humic gas in early high mature stage, and over matured gas Thus according to nature gas carbon isotope characteristics, combined with other corresponding research achievements, the author reveals that Qianmiqiao buried hill gas pool is specially characterized by its multistage, composite hydrocarbon accumulation.
In the study of natural gas genesis and exploration, it is still our major task to determine effective hydrocarbon source rocks and accumulation assemblage. In terms of primitive basin, the low limit of organic carbon in effective hydrocarbon source rocks (whether carbonate rock limit or shale) is 0.5%. While in polycyclic superimposed sarsen basin, this value is not suitable to secondary hydrocarbon generation. The limits of secondary hydrocarbon generation in different maturation stages are as follows: when Ro is 1.0%～1.2%, the limit is 1.0%; when R-o is 1.2%～2.0%, the limit is 2.0%; when Ro is 2.0%～3.0%,the limit is 4.0%; While when Ro is more than 4.0% and H/C is less than 0.3, there are little probability to find gas reservoir regardless organic carbon abundance. The other effective hydrocarbon sources are reservoir bitumen and local residual liquid hydrocarbons in palaeoreservoirs. They can crack into light oil pools and gas reservoirs. And a few of these secondary pools were reformed once again into late gas reservoirs. So, the distribution of secondary reservoirs are d
etermined by effective hydrocarbon source rocks and center superposition of generation and migration of effective hydrocarbon sources.
Static correction and choosing datum are the key factors that directly affect the quality of the image when processing the seismic data acquired in Chinese northwest with complicated surface conditions. According to the experience of processing the land seismic data in recent years, the method of combination the surface parameters investigated in the field and refraction static correction is put forward. Firstly, atripping the layer with low-velocity to the top interface of the first layer with high velocity. Secondly, correcting the data to a final datum. Thirdly, separating the static correction values into two components, the long-wave length part and the short-wave length part. And then using the velocity derived from the CMP datum to stack the seismic data. Finally, migrating the stack data in the final datum, then the migration datum can be solved correctly in this way. Frankly the very way to solve the static correction accurately is tomigrate the data from the surface in depth domain.
Kela 2 gas field is the biggest land monoblock dry gas reservoir which has been discovered in China so far It is essential to make it a high productivity gas field as it is the main production area of "West|East Natural Gas Transportation" Project Kela 2 gas field is an overpressure reservoir The formation pressure of this gas field is very high (74 36 MPa) And its pressure parameter is as high as 2 or more During the natural depletion, the overpressure formation rock will stand the net weight above as reservoir pressure is getting lower and lower. And great plastic deformation would occur in the formation rock. Such characteristics as permeability, porosity and compressibility factor will decrease. And it would negatively affect gas production. And so, during the development of Kela 2 gas field, rock deformation is a watchful problem for production capacities.This paper is to research the overpressure rock deformation characteristics of Kela 2 gas field and its effects on gas production according to rock coverage experiment.
In the stage of exploration, to make good evaluation of the reservoir characteristics, to decrease exploration risk and investment, it is necessary for us to erect a geological knowledge base in order to make disadvantage of the lack of data. This is because, in this stage, there may has bad ground conditions, sophisticated underground geological situations and rare wells. To do this, suitable outcrops should be selected as the experimental area of the field reservoirs. By the analysis of the outcrop profile and the sedimentary face correlation,we can make sedimentary models so that the distribution of faces in different time can be defined. At the same time, the tracing of the sandstone outcrop in the profiles and the analysis of the compositional factors can make the models of the original sandstone framework. Subsequently, with the combination of logging and drilling data, the geological prediction model of reservoirs can be made through the random modeling method. On doing this, prediction of the sandstone superimposition between different wells in space and the interbed distribution rules can be realized on account of certain geological laws. Kuche depression is located in front of Tianshan mountain. The tectonic and ground conditions are very complicated; seismic imaging in the mountain areas and signal-to-noise ratio are low; drilling in these areas is of unexceptionally difficult. Due to all of these reasons, it is very important to make geological models of reservoirs. This method has been used in the reservoir description in Kela 2 gas field successful
ly. For the evaluation of the reservoir quality and potentiality in the gas field, it is a reliable method.
Though the comprehensive analysis of rock cores, well logs and seismic data, and under the guidance of the theory of high|resolution sequences stratigraphy, the stratigraphic sequence of Shan 1 section in the Da Niudi gas field has been identified and analyzed. The results show that the Shan 1 formation belongs to the river-delta sedimentary system, of which braid river delta developed better. In this sedimentary circumstance, three types of sumper-short-term cycle sequences can be distinguished, and four short-term cycle sequences can be indentified. And further, the chronostratigraphic sequence framework has been constructed, which has great application significance in the fine gas description.
The project"west gas transporting to east China" is the great project, which plays an important role in developing the west economy, optimizing the energy constitutions, improving the environment and so on. Based on the analyses of gas reserves in the Tarim basin, the present natural gas reserves of the Tarim basin can only support thirteen year supplies according to the gas ration 120×108 m3 for one year. The lack of petroleum resources forces us to seek other possible sources. Petroleum resource abroad is the possible one. For the petroleum safe strategy and country safe strategy, the natural gas from Russia and Mid-Asia is the favorable one. We must construct the continental gas pipeline from Russia and Mid-Asia which can connect with“west gas transporting to east”.
甘公网安备 62010202000678号
