The Study On The Geological Modeling Of DongHe Sandstone Member In The Donghe I Carboniferous Oil Reservoir

The Donghe 1 carboniferous oil reservoir is located at the Donghetang riftzone anticline tectonic belt in the middle section of the North Tarim Uplift. Donghe Sandstone belongs to the foreshore and beach shoreface microfacies of wide sea-based deposition, average sedimentary thickness is 250m, the overall evaluation on reservoir is medium porosity and permeability, reservoir type is the block bottom water oil reservoir. Until November 2010, the cumulative oil production of reservoirs is 794.2417×10⁴t, the cumulative water injection is 1484.0×10⁴m³, and the water cut is 52.12%.There is the following problems now. Due to the large thickness of the reservoir, part of lithologic section division needs some further implementation. The development of vertical sandwich made reservoir heterogeneity serious. Beacause of heavy oil section in the bottom of reservoir, it is needed to figure out the distributional characteristics of heavy oil section and impact of heavy oil section for reservoir development. The contradiction between layers becomes more prominent when the water cut rises rapidly in the later development of reservoir and so on. To solve these problems, we must clearly understand reservoir characteristics of the region to establish the geological model which can accurately reflect the characteristics of reservoir geology. It is very significant for the adjustment for the later development programs.In this paper, on the bases of the actual situation of the Donghe 1 carboniferous oil reservoir, combing with the drilling, coring, core laboratory analysis, and dynamic performance data, it is researched on the reservoir fine contrast, reservoir characteristics, heavy oil distribution and its influence on the development. Based on previous research, it is established three-dimensional reservoir stochastic model, calculated the geology reserves and reserves of heavy oil section. In the paper, there are the following obtained results and understandings:(1)Donghe Sandstone section is divided into the upper and lower parasequence set, of which the lower part of parasequence sets belong to the fall deposition of sea level and the upper parasequence set belong to the deposition of the sea-level rising or sea into the land back to the plot. On the basis of divisons on parasequence set , Donghe Sandstone is furtherly divided into 5 parasequences and subdivided into 10 strata groups (lithologic).(2) Sandstone reservoir section is divided into five categories: ClassⅠis porosity>18%, permeability>100×10^-3 m²; ClassⅡis porosity of 17%¹8%, permeability of 50×10^-3 m²¹00×10^-3 m²; ClassⅢis porosity of 14%¹7%, permeability of 10×10^-3 m²⁵0×10^-3 m²; ClassⅣporosity of 10%¹4%, permeability of 3×10^-3 m²¹0×10^-3 m²; ClassⅤof non-reservoir is porosity <10%, permeability <3×10^-3 m². The lithologic Section 1 is low porosity and low permeability, and mainly belongs to class reservoir IV. The lithologic Section 2, 3,4 and 5 is medium porosity and medium permeability, and mainly belongs to class reservoir III which is the main producing layers. The lithologic Section 6, 7,8 and 9 are medium porosity and low permeability and the main section is the water layer.(3) The Sandwich of sandstone section is divided into three categories: muddy sandstone Sandwich, gray sandstone sandwich and muddy gray sandstone sandwich. The main classes are muddy sandstone Sandwich and muddy gray sandstone sandwich which are more developed in the entire Donghe sandstone, but the gray sandstone sandwich is the least developed and its distribution is random and thinner.(4) Heavy oil segment of Donghe Sandstone is characterized by logging response: The amplitude difference is large among Resistivity of flushed zone RXO, the lateral resistivity RM and deep lateral resistivity RD, resistivity of heavy oil is between the oil layer and water layer. The thickness of heavy section is of 10m¹5m and the average thickness is about 11.54m. It is indicated that heavy oil segment in the bottom of Donghe sandstone plays a significant inhibition for the forward edge and bottom water of the reservoir by analysis of reservoir pressure and water injection wells profile.Finally, formation model of the Donghe sandstone in Donghe 1 Oilfield is established by the above results. According to the results of this model, geological oil reserves is 25.566 million tons and the reserves of heavy oil section is 2.559 million tons.