Dongpu Depression Fractured Shale Oil And Gas Reservoir Characteristics And Identification Technology

Mudstone-fractured petroleum pools, a kind of concealed pool, mainly represent those pools whose petroleum produced from fractures and micro-pore of mudstone. The kind of pools or reservoirs were found long age. Until several years ago, mudstone-fractured reservoirs were discovered in Dongpu Depression. And this developed new areas of petroleum exploration for Zhongyuan Oil Field.Now many problems appeared in exploration and exploitation of mudstone-fractured petroleum pools. To solve these problems, characteristics of the kind of pools were contrasted, and all sorts of data from geology, drilling, logging, testing and indoor analysis were studied. In the study, we applied lots of theories and techniques from different disciplines, mainly including geotectonics, sedimentology, petroleum geology, petroleum geochemistry, drilling geology. Based on analysis of the showing well on mudstone-fractured reservoirs at Wenliu Area in Dongpu Depression, the sedimentary characteristics, porosity & permeability features and distribution laws of the most important formation, the third segment in Shahejie Formation of Paleogene system( Es~3), were researched. Then the factors which had controlled the formation of mudstone-fractured reservoirs were discovered. At last, the identification skills were concluded.For theory research and technology or technique development, much constructive work was done in the study, and the following is representative.1. With sedimentary disciplines, we analyzed the distribution rules of main salt rock segments in Dongpu Depression, deduced the formation-controlling factors anddistribution rules of salt rocks, and pointed out the favoring productive blocks and strata of salt rocks among Shahejie Formation (Es Fm.) , Wenliu Area.2. Subjecting to correlation theories of petroleum geology & geochemistry, we tested oil-bearing samples by organic geochemical means, and found that petroleum from mudstone-fractured reservoirs was mainly originated from the stage of thermo-evolution to ripeness of source rocks in Es3. Based on this, we discovered the formation-controlling factors of mudstone-fractured reservoirs, which included good source, favoring sedimentary fades, abnormal high-pressure zone and fracture distribution. Then enriched and productive mode of mudstone-fractured reservoirs was set up.3. According to the enriched and productive mode of mudstone-fractured reservoirs and development features of formations of Wenliu Area, salt rocks are found in Es32, Es33 and Es34; between the salt rocks are tens of layers dark clay stones, calciferous mudstones etc. with stable thickness and highly organic abundance. These source rocks have good type and promising abundance value of organic matter. Now the mudstones are coming within the stage of mainly generating hydrocarbon, sealed by salt rocks with excellent preserving conditions, and easy to form abnormal high-pressure, so they are the promising bed set to find mudstone-fractured reservoirs; and the distribution zone of abnormal high-pressure is promising zone to find this kind of reservoirs. In district without salts, thick mudstones are found in the upper formations of Es32 and Es33, and it is favoring to form mudstone-fractured reservoirs.4. Depended on the study of genesis and controlling factors, the petroleum accumulation rules were approached: based on sedimentary combination and thickness, it is the faults that controlled enrichment level of petroleum. Generally speaking, in the district with salt rocks, when the thickness of mudstones is 20-50 m, the calciferous and gypsum-bearing mudstones with a monolayer thickness about 5m, thus the high near profile of normal faults should be enrichment zone of petroleum. The zone is also promising place for following exploration of mud with fractures.5. In terms of realization on characteristics and formation conditions of mudstone-fractured reservoirs, we treated the identifying and evaluating methods separately using mud-logging and well-logging, founded corresponding identifying or evaluating standard, and pointed out the promising targets of this kind of reservoirs in research area. The work included: 1 ) based on the conclusion of integrated interpretation, set up mud-logging standard for the interpretation of mudstone-fractured reservoirs, and pointed out that the promising prospects in Wenliu Area were Es32 of Wen300 Block, Es32 of Wen39 Block and Es34 of Xinwen401 Block; 2 generalized well-logging characteristics of mudstone-fractured reservoirs, quested a set of well-logging interpretation methods for the mudstones with fractures, developed a correlative computer program, and forecasted that the favoring blocks of mudstone-fractured reservoirs were south to Wen300 Block, north to Wen 104 Block, south & southwest to Wen 104 Block and north & east to Xinwen401 Block.