The Depositional Architecture Study Of Pu-1 Oil Layer And Its Application To Methods Of Blockage-removing And Stimulation Of Polymer Injection In Chunxi Of Shabei Developing District

Pu-1 oil layer, one of most important productivity layers, composed with lower part of Cretaceous Yaojia Formation and upper part of Qingshankou Formation, is river and delta sedimentary. At present, parts of area has been carried out polymer injection development. After the third development, there is still about 50% remaining oil undevelopment. Through the detailed study of depositional architecture of reservoir sandbody, confirming the heterogeneity characteristic, and revealing the distribution law of remaining oil and the polymer injection blocking mechanism have great significance of theory and practice in later development period. Applying high-resolution sequence stratigraphy theory and Miall's genetic architecture analysis method, the sedimentary architecture of sandbody, remaining oil distribution law, polymer injection blocking mechanism and feasible methods of blockage-removing and stimulation of polymer injection of Pu-1 oil layer have been studied in this paper. There achieved the following results:1. The high-resolution sequence stratigraphy framework of Pu-1 oil layer has been estabilished,and divided 3 4^th order sequences and 7-8 5^th order sequences. Several sedimentary microfacies have been recognized under the high-resolution sequence stratigraphy framework, such as delta plain, delta front, river and so on. The sedimentary microfacies mapping of 4 order sequence revealled the laterial change of sedimentary microfacies and sandbody thickness.2. we summarized the sandbody types, including singe genetic sandbody and composed sandbody, and expatiated the sedimentary and reservoic characteristic of the normal rhythm, reverse rhythm and composed rhythm sandbody in this paper. The depositional architecture study of Pu-1-2 and Pu-1-3 composed sandbody has also been carried out, and show that the shape, distribution and recognization characteristic of 4^th order surface in Miall's genetic architecture unit analysis, which formed of Pu-1-2 mender single point bar laterial superposition. Pu-1-3 incised braided channel formed during the sea-level falling period, and formed erode and filling configuration, by which the 3^th or 5^th surfaces can be identified.3. According to the vertical superposition of composed sandbody and horizonal heterogeneity of reservoir, there has been divide into 3 different sedimentary belts,that is major channel belt, channel margin and mouth bar belt and marginal sand bar-flooding fan -flooding plain belt, and discussed the different remaining oil distribution characteristic. The interlayer distribution and remaining oil distribution model controlled by 4* order surface of Pu-1-2 and Pu-1-3 composed sandbody have been summarized in this paper.4. The fieldwork and laboratory experience revealed the composition and the blocking process. The relationship of reservoir heterogeneity and blocking has been discussed. The result show that normal rhythm sandbody is hardly blocked or near blocked, the blocking mainly is mud and mechanical fabric, that is connected with the polymer power quality and mix rate. The reverse rhythm and composed sandbody is far blocked, the blocking is mainly inorganic inside and organic arrounding, that is connected with porosity and permeability. There can be divided 3 permeability distribution belts, that are over 500md, 300-500md and lower 300md. There is hardly blocking or nearly blocked in the over 500md belt, there is easy far blocked in the 3OO-5OOmd belt, and there is easy blocked in the lower 300md belt. These belts are almost consistent well to the main channel belt, channel margin-mouth bar belt and marginal sand bar-flooding fan-flooding plain belt5. According to the different blocking characteristic of different depositional architecture in polymer injection development, the feasible methods of blockage-removing and stimulation of polymer injection have been brought in this paper. Applying HRS new type blockage to normal rhythm nearly blocking sandbody, applying colophony sand to composed and far blocking sandbody, and applying crush and blockage to complex interlay thick sandbody.