Major discoveries of natural gas have recently been made in the oolitic dolostones of the Early Triassic Feixianguan Formation in NE Sichuan Province, Southern China. These dolostones were formed by three facies‐controlled dolomitization processes: (i) meteoric mixing zone dolomitization with dolomites having a relatively high degree of crystalline order (δ13C:−1.0 to 2.5%PDB; δ18O:−6.5 to −2.5%PDB); (ii) seepage‐reflux dolomitization associated with evaporative brines; the corresponding dolomite crystals are relatively ordered and were formed in tidal flat environments and platform‐margin oolitic shoals adjacent to lagoons; (iii) burial dolomitization (shallow to moderate burial depths, ca. 1,000 to 4,000m), whereby seawater‐derived brines were present in the host rock and the resultant water/rock reactions played a major role in dolomitization. The three dolomitization processes were controlled by the arid climate prevailing during the Early Triassic, and also by fourth‐order relative sea‐level changes, especially with respect to the reflux dolomitization. Burial dolomitization, which is of second‐order of importance for porosity development, was strongly dependant on the presence of sufficient original porosity to facilitate water‐rock reactions within the carbonates. The best reservoir rocks formed as oolitic banks and bars in the vicinity of evaporative lagoonal‐tidal complexes which experienced optimal conditions for dolomitization. Dolostones with a dolomite content of 80% to 90% form good vuggy reservoir rocks at the present day, indicating that the intensity of dolomitization influences the quality of reservoir rocks. According to our results, future gas exploration in the Feixianguan Formation dolostone reservoirs should focus on locating oolitic banks associated with evaporative lagoon and tidal flat complexes and delineating the best structural/lithological traps.

Modeling the elastic properties of organic shale has been of long-standing interest for source rocks and unconventional reservoir characterization. Organic shales exhibit significant variabilities in rock texture and reservoir properties at different maturity stages, subsequently affecting their elastic responses. We have developed a new rock-physics modeling scheme honoring the maturity levels (immature, mature, and overmature), which are constrained by the evolution of the physical properties of organic shale upon kerogen maturation. In particular, at different maturity stages, the manners in which the compliant organic materials interact with the inorganic mineral matrix are characterized by different effective medium theories. On the basis of the developed rock-physics templates, organic shales have different elastic behaviors at different maturity stages. Ignoring the impact of kerogen maturation is insufficient to adequately characterize the elasticity of the whole organic shale system. Modeling results suggest that the elastic responses of organic shale are sensitive to two dominant factorsorganic matter content and mineralogical composition. The elastic anisotropy characteristics are not only affected by the kerogen content and clay alignment but also depend on the morphology of kerogen distribution. Our results compare satisfactorily with data from ultrasonic velocity and log measurements, confirming validity and applicability of our modeling framework.

As the OCR technique is not yet adequate for handwritten scripts with large lexicon, word spotting has been introduced as an alternative to OCR. This paper proposes a novel approach to word spotting that, instead of matching features of the word image to features extracted from predefined templates, uses the estimated posterior probability as the output of well trained classifier for spotting. Gabor features are extracted from gray scale image in order to yield higher performance on degraded, low quality document image.

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