The grain size analysis of fifteen specimens from Honghuatao Formation in Dangyang area at the northwestern boundary of Jianghan basin shows that their average diameters, sorting coefficients, skew coefficients and kurtosis coefficients are mainly in the same range, and they bear similar frequency curves of grain size with double peaks and similar probability cumulative curves with an obvious pattern of three segments. Basing on this and referring to the equation of sedimentary dynamics, comparative analysis was done by both hydrodynamic concept and aeolian force concept in this article. A conclusion was drawn that the genesis of sands in the Honghuatao Formation at the northwestern boundary of Jianghan basin was aeolian deposit, locally influenced by broken streams.
The South Slope District of the Mahu Depression in the Junggar Basin, a major favorable zone for middle and superficial oil–gas exploration, has experienced industrial gas flow. However, research on the sedimentary microfacies characteristics of Segment 2 of the Sangonghe Formation, the main oil-bearing formation, remains lacking. In this study, the rock type, sedimentary tectonics, and sedimentary microfacies of Segment 2 of the Jurassic Sangonghe Formation in the South Slope District of the Mahu Depression were thoroughly investigated through 3D seismic, rock core, and logging data. Moreover, the sedimentary modes and distribution characteristics of the sand bodies in the study area were further analyzed. Results showed that subfacies at the front edge of the braided river delta are developed at Segment 2 of the Sangonghe Formation, which can be further divided into four microfacies types, namely, underwater distributary channel, sheet sand, estuary dam, and interdistributary bay. The estuary dam is only developed at local positions in the work area. The vertical evolutionary laws from Segment 2 of the Sangonghe Formation to Segment 3 of the Sangonghe Formation are explicit and manifest as retrogradation from the subfacies at the front edge of the braided river delta to the prodelta. The sand bodies formed by frequent swings of the underwater distributary channels are the main reservoir bodies, and the lithology is mainly fine-grained feldspar lithic sandstone, and sedimentary tectonics have diverse forms. On the basis of deposition microphase analysis, the sand bodies’ planar distribution characteristics under phase-controlled conditions were analyzed using a seismic model inversion technology to provide theoretical guidance for oilfield expansion, exploration, and exploitation.
The baseline and level data for 36 years at Dahuichang observation site are systematically studied in this paper. These observation data are resolved into horizontal and vertical components of fault slip. Based on the relation between fault slip and the direction of compressional stress in North China, we reveal the stress regimes and faulting characteristics among Babaoshan Fault Zone (Dahuichang segment) during the periods of Xingtai, Tangshan and Zhangbei-Datong earthquakes. We conclude that study on the deformation data should be carried out not only by mathematic processing and statistics analysis, but also by geological interpretation based on faulting pattern and stress regimes, in order to understand how fault slips during the development of earthquakes.
The type of Palaeokarst reservoir space is complex, which is difficult to be recognized and predicted. Study shows that the pore space of this kind of reservoir is mainly consisted of caves, fracture, fracture and vugs. In connection with 4 types of pore spaces, a physical model is designed to simulate seismic reflection characters and conduct forward simulation. The result of study shows that when the velocity is very low in the cave, obvious diffraction can be observed on single-shot and stack profile, and stronger short axis reflection is represented on 2D stack profile, the fracture growing belt is obvious abnormal on seismic reflection with “chaotic” reflecting property. Strong beaded reflection appears near the cross-over position of multi-group fractures and vugs, vug reservoir represents a stronger discontinuous reflection on seismic profile.
This article builds up the computational models of the minimum oil-bearing area, development investment, development profit, economic feasibility, decline rules, and economic reserve scale of deep low-permeability reservoirs. Study shows that the minimum oil-bearing area of the marginal reservoir is 0.02 km2; the economic threshold production is affected by reservoir burial depth, price of the crude oil, and operation cost of per ton of oil, of which burial depth and crude oil price are the sensitive factors affecting the economic production capacity; minimum reserve scale is affected by burial depth, recovery and consumption price of the crude oil and the operation cost of per ton of oil, of which burial depth and the consumption price of the crude oil are the sensitive factors affecting the economic reserve scale. Because of the increasing crude oil price, the original low efficiency or invalid reserves could be reestimated as the economic ones. The reservoir Es36–7 of the block Wei 360 is on the edge of the economic development.
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