油气勘探风险评价与决策技术研究

PetroChina and other national petroleum incorporations need rigorous procedures and practical methods in risk evaluation and exploration decision at home and abroad to safeguard their international exploration practice in exploration licence bidding, finding appropriate ratio of risk sharing with partners, as well as avoiding high risk projects and other key exploration activities. However, due to historical reasons, we are only at the beginning of a full study and methodology development in exploration risk evaluation and decision. No rigorous procedure and practical methods are available in our exercises of international exploration. Completely adopting foreign procedure, methods and tools by our national incorporations are not practical because of the differences of the current economic and management systems in China. The objective of this study is to establish a risk evaluation and decision system with independent intellectual property right in oil and gas exploration so that a smooth transition from our current practice into international norm can take place. The system developed in this dissertation includes the following four components: 1. A set of quantitative criteria for risk evaluation is derived on the basis of an anatomy of the parameters from thirty calibration regions national wide as well as the characteristics and the geological factors controlling oil and gas occurrence in the major petroleum-bearing basins in China, which provides the technical support for the risk quantification in oil and gas exploration. 2. Through analysis of existing methodology, procedure and methods of exploration risk evaluation considering spatial information are proposed. The method, utilizing Mahalanobis Distance (MD) and fuzzy logic for data and information integration, provides probabilistic models on the basis of MD and fuzzy logic classification criteria, thus quantifying the exploration risk using Bayesian theory. A projection of the geological risk into spatial domain provides a probability map of oil and gas occurrence in the area under study. The application of this method to the Nanpu Sag shows that this method not only correctly predicted the oil and gas occurrence in the areas where Beibu and Laoyemiao oil fields are found in the northwest of the onshore area, but also predicted Laopu south, Nanpu south and Hatuo potential areas in the offshore part where exploration maturity was very low. The prediction of the potential areas are subsequently confirmed by 17 exploration wells in the offshore area with 81% success, indicating this method is very effective for exploration risk visualization and reduction. 3. On the basis of “Methods and parameters of economic evaluation for petroleum exploration and development projects in China”, a ”pyramid” method for sensitivity analysis was developed, which meets not only the need for exploration target evaluation and exploration decision at home, but also allows a transition from our current practice to international norm in exploration decision. This provides the foundation for the development of a software product “Exploration economic evaluation and decision system of PetroChina” (EDSys). 4. To solve problem in methodology of exploration decision, effort was made on the method of project portfolio management. A drilling decision method was developed employing the concept of geologically risked net present value. This method overcame the dilemma of handling simultaneously both geological risk and portfolio uncertainty, thus casting light into the application of modern portfolio theory to the evaluation of high risk petroleum exploration projects.

知觉组织在拥挤现象中的作用

Crowding, generally defined as the deleterious influence of nearby contours on visual discrimination, is ubiquitous in spatial vision. Specifically, long-range effects of non-overlapping distracters can alter the appearance of an object, making it unrecognizable. Theories in many domains, including vision computation and high-level attention, have been proposed to account for crowding. However, neither compulsory averaging model nor insufficient spatial esolution of attention provides an adequate explanation for crowding. The present study examined the effects of perceptual organization on crowding. We hypothesize that target-distractor segmentation in crowding is analogous to figure-ground segregation in Gestalt. When distractors can be grouped as a whole or when they are similar to each other but different from the target, the target can be distinguished from distractors. However, grouping target and distractors together by Gestalt principles may interfere with target-distractor separation. Six experiments were carried out to assess our theory. In experiments 1, 2, and 3, we manipulated the similarity between target and distractor as well as the configuration of distractors to investigate the effects of stimuli-driven grouping on target-distractor segmentation. In experiments 4, 5, and 6, we focused on the interaction between bottom-up and top-down processes of grouping, and their influences on target-distractor segmentation. Our results demonstrated that: (a) when distractors were similar to each other but different from target, crowding was eased; (b) when distractors formed a subjective contour or were placed regularly, crowding was also reduced; (c) both bottom-up and top-down processes could influence target-distractor grouping, mediating the effects of crowding. These results support our hypothesis that the figure-ground segregation and target-distractor segmentation in crowding may share similar processes. The present study not only provides a novel explanation for crowding, but also examines the processing bottleneck in object recognition. These findings have significant implications on computer vision and interface design as well as on clinical practice in amblyopia and dyslexia.