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Free gas saturation is a key parameter for calculating shale gas reserves. The complex conductivity mechanism of shale reservoirs restricts the application of Archie's formula and its extended form for the evaluation of free gas saturation. Instead, a number of non-resistivity-based saturation evaluation methods suitable for shale gas reservoirs have been established, including core calibration (TOC method, clay content method), gas porosity cutoff, excavation effect and four-pore modeling. These methods, together with adsorbed phase porosity correction, are used to calculate the free gas saturation. These methods are applied to shale reservoirs of the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Sichuan Basin, southwestern China to test their applicability and accuracy. The results, when compared with measured data from core samples, show that the TOC-based core calibration is more accurate in evaluating free gas saturation in the entire shale gas interval, which is of great significance to the calculation of shale gas reserves. [ABSTRACT FROM AUTHOR]

K reservoir is an important oil and gas producing layer of H oilfield in the Middle East, Iraq. The reservoir space is mainly matrix pores and dissolved pores, with a wide range of permeability and poor correlation between porosity and permeability. The reservoir thickness is large, and the stratigraphic heterogeneity is very strong; therefore, it is poor quality to identify carbonate reservoir fluid properties only relying on conventional logging data and traditional logging evaluation methods. Aiming at this problem, the fluid identification work of K reservoirin H oilfield was carried out. By analyzing conventional logging data, it is found that the ratio of deep to shallow resistivity can better distinguish water from hydrocarbon. Based on analyzing morphological characteristics of the total hydrocarbon curve and corresponding reservoir fluid properties, it is found that the gas curve has obvious differences in the morphology of different fluid properties, so it is considered to further classify water and hydrocarbon by using gas curve. It is found that the ratio of heavy hydrocarbon tohydrocarbon gas density index can better classify oil-water layer and water layer. In order to quantitatively characterize the identification process, the identification method of water-oil-water layer gas measurement curve (ECR1) is established. ECR1 greater than 0 is oil-water layer, otherwise, it is water layer. Based on gas wet index, light hydrocarbon ratio and excavation effect, the identification method of gas-reservoir gas measurement curve (ECR2) is established. ECR2 higher than 0 isgas reservoir, and vice versa. The application of this model to 38 small layers in 13 wells of K reservoir in H oilfield shows that the recognition coincidence rate reaches 81.58%, and the recognition accuracy is high, meeting the actual needs of study area. The established ECR model has achieved good application effect in K reservoir of H oilfield, which can provide a certain reference for the subsequent exploration and development of this area, and also provide a reference for fluid identification of similar carbonate reservoirs worldwide.

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the Yingdong Oil/Gas Field of the Qaidam Basin, multiple suites of oil-gas-water systems overlie each other vertically, making it difficult to accurately identify oil layers from gas layers and calculate gas-oil ratio (GOR). Therefore, formation testing and production data, together with conventional logging, NMR and mud logging data were integrated to quantitatively calculate GOR. To tell oil layers from gas layers, conventional logging makes use of the excavation effect of compensated neutron log, NMR makes use of the different relaxation mechanisms of light oil and natural gas in large pores, while mud logging makes use of star chart of gas components established based on available charts and mathematical statistics. In terms of the quantitative calculation of GOR, the area ratio of the star chart of gas components was first used in GOR calculation. The study shows that: (1) conventional logging data has a modest performance in distinguishing oil layers from gas layers due to the impacts of formation pressure, hydrogen index (HI), shale content, borehole conditions and invasion of drilling mud; (2) NMR is quite effective in telling oil layers from gas layers, but cannot be widely used due to its high cost; (3) by contrast, the star chart of gas components is the most effective in differentiating oil layers from gas layers; and (4) the GOR calculated by using the area ratio of star chart has been verified by various data such as formation testing data, production data and liquid production profile.

The change in the stress state of the underground rock caused by excavation is the root cause of the deformation instability. Compensating for the stress change is one of the keys to effectively control the instantaneous deformation of rockbursts and the slow deformation of soft rocks in deep underground engineering. At present, the Platts pressure arch theory and the New Austrian Tunneling Method are commonly used in ground control, but their applicability to high-stress deep rock masses is limited. The strength and elongation of the traditional support materials are insufficient, the prestress is low, and it is difficult to effectively control the large deformation of deep rock masses. In this work, the excavation effect and support compensation effect of the rock are analyzed from the mechanics perspective, and an excavation compensation method suitable for controlling large deformation of deep rocks is proposed. The excavation effect verification experiments are carried out to examine the large deformation failure characteristics. Based on the excavation compensation method, a high prestress excavation compensation control technology is developed by using a new Negative Poisson's ratio (NPR) material. This technology is successfully applied to deep buried hard rocks and soft rocks to realize the effective control of the large deformation, which proves the applicability of the excavation compensation method and technology. • The excavation effect and support compensation effect of the rock mass are analyzed. • The mechanical properties test on the NPR anchor bolts (cables) is carried out. • An excavation compensation method suitable for controlling deep rock mass is proposed. • Excavation compensation method and new NPR material are applied to engineering. [ABSTRACT FROM AUTHOR]