Ordos Basin Kawaguchi - The Laoshan Oil Chang - 6 Reservoir Logging Oil Assessment

Chang 6 oil reservoir group is the main oil exploration horizon of Chuankou-Laoshan oil area which lies in the southeast of northern Shaanxi slopes of the Ordos Basin. The chief oil reservoir type of the study area is lithologic reservoir of low porosity and low permeability. Except for conventional sandstones, there are still some highly radioactive sandstone and a few Carbonate-rich sandstones. It's a little difficult to evaluate the oiliness in the reservoir with logging because of the complexity of the lithology, poor physical properties on the whole, the existence of micro-fracture and the complexity of oil-water relationship. In view of the difficulty, this article is aiming to find that how to evaluate the oiliness characteristics of the reservoir in the study area validly and exactly.On the basis of the collection of the data about well drilling, mud logging, log presentation, laboratory experiments, oil testing and water testing and familiarization to the geological background of the study are, the author carries out the research on the oiliness characteristics by using related logging data and geological data, and then analyzes the influence of the deposition, layer, lithology and physical properties in the reservoir to the oiliness characteristics and their changes in further. The article mainly makes comparison and analyzes the differences of gamma ray curve response characteristics and acoustic slowness log response characteristics between conventional sandstones and highly radioactive sandstones, the changes of logging response characteristics in the reservoirs with different pore structures and the response characteristics of log presentation when the content of carbonate changes. Based on the relationship characteristics of the four properties in the reservoir, and pertinent to the different logging response characteristics of conventional sandstones, highly radioactive sandstones and Carbonate-rich sandstones, the article establishes the porosity logging interpreting models and identifies the oil layer, water layer and dry layer intuitively and fast by multi-skills of overlapping maps and cross-plot maps. With the analysis data of rock-electricity experiment, the water receptivity from the contrasting plates of formation water's concentration mineralization and the ultimatum of Archie's formulas, we can calculate the oil saturation of the reservoir quantitively.