| The petroleum exploraion prospective in deep burial strata is an issue concerned on petroleum industry all over the world. It involves in some important problems, such as finding new petroliferous strata or fields by exploring deeper buried strata. Bonan sag is one of the key targets of the Jiyang depression's deep buried strata. But during long time, it is very difficult for the exploration and development of sandstone oil layers on the upper part of the fouth member of Shahejie Formation. It is mainly represented as it can't be got the optimum production test effect and can't keep long term rate-maintenance. Research shows that the production problem is related to serious reservoir heterogenity, which is dominated by the distribution of depositional facies. The aim of the paper is to build 3D geological model, including depositional facies model, lithology model, petrophysical models such as porosity model and permeability model. These models will help reservoir engineer to further understand the distribution of reservoir heterogenity of the upper part of the fouth member of Shahejie Formation.During the development and deposition about the fouth member of Shahejie Formation, Bonan sag is under the condition of arid to semiarid climate. During this period, Bonan sag was a half graben which is steep in the northeast and gentle in the southwest. The distribution of depositional facies in Bonan sag is very complex, which include five depositional systems, such as salt lake of deep water, transgressive fan delta, proximal turbidite fan, slump turbidite fan, distal turbidite fan. From lower to upper, deliverability of supply source debris rappidly reduced, the result is that the scale of the fan deltas rappidly lessened. The direction of supply source has slightly varied from NNE to NEE in different phases. Vertically, a series of turbidite fans and fan deltas developed along eastern border of Guxi contemporaneous fault zone and sandbodies were overlaped with each other.Applied the high resolution sequence stratigraphy theory, the upper part of the fouth member of Shahejie Formation is carried on the fouth order sequence classification and correlation. The research shows that with the time goes by, structural relief is smaller and accommondation is smaller as well. Topography of basin becomes to be simple. Four dispersed sub-sag grown to one sag (Boshen 5 sag), which reflected the process of rift stage converted to rift shrinking stage. At the same time, structural strike varied from N W-SE to NE-SW.With diagenetic evoluation analysis, there are three secondary porosity zones, two of them located in the upper part of the profile whose porosity is small, the other one is located in the lower part whose porosity is up to 10% -18%.Controlled by the fouth sequence boundary, with chronostratigraphic modeling research with Gridstat Pro software, some models such as depositional facies model, lithology distribution and reservoir quality model(include porosity, permeability and productivity ratio) have been built.From comprehensive analysis, the conclusion can be drawn that the favorable reservoir of the upper part of the forth member of Shahejie Formation of Bonan sag is the outer fan sandbody of fan delta near the Y159 of the eastern part of the sag, the middle fan and outer fan of Y160, midian fan and distal fan of proximal turbidite and slump turbidite. Vertically, the upper sand body is more favorable. Though the sand of the lower part of the profile is more developed, the salt lake of deep water facies is undeveloped, which is disadvantage for the petroleum's congragation.
|
PDF Full Text Request