Drilling Comlex Analysis And Risk A Ssessment Studies Of Yuanba Area

Petroleum drilling is a secret underground project, with a lot of complicated and uncertain factors, Yuanba area has ancient stratums and complicated structures, the situations like "spray, leak, collapse, cards, oblique, hard, poison, jumping drills, drill breaking" exist normally, stratums in wells which have the same structure, with the outstanding personality and poor analogy, even for the near wells, the data is also hard to be referred to, there are many unpredicted factors in the drilling construction. Therefore, researching the recent all kinds of drilling complicated situations in Yuanba area, studying and analyzing the reason of complicated situations, carrying out the evaluate research of drilling risk in Yuanba area, supporting references and experience for the safe drilling design and construction of gas field to reduce the possible risk in process of drilling, which is of significance to the safe and quick exploration and development in Yuanba area natural gas field.Drilling is one of the most important means in petroleum and natural gas exploration and exploitation. During the drilling operation, drilling complex incidents and accidents are the threat to the entire process of drilling, which have a serious impact on the drilling speed,quality and economic benefits. It can be summarized from the lessons of drilling accidents many years that the main reasons are the no timely find of the precursor of drilling complex incidents, the inaccurate judgment and process of the drilling accident type. For the current situation of oilfield development and problems in drilling operation, the inaccurate reasoning model based on the certainty factor is used to establish the drilling complex incidents and accident diagnosis based on expert system.Firstly, the knowledge base of drilling complex incidents and accidents is established, through which a large number of empirical knowledge of the domain experts and field technicians are stored in the computer completely and rationally. Not only the changing conditions of drilling complex incidents are required to adapt, including the prevention and treatment programs to the drilling complex incidents, but also the well drilling services are needed for the diagnosis of drilling complex incidents. Secondly, the drilling complex incidents and accident diagnosis based on expert system is proposed in the paper. In the design process of expert system, the program implement module of knowledge is taken as the reasoning machine to establish the inaccurate reasoning model based on the certainty factor. Comprehensively considering the uncertainty value of evidence and the uncertainty factor of rules, the uncertainty value of final conclusions can be calculated and therefore the judgment and decision can be made accordingly.It can be found from the analysis of case study of drilling accidents that the system can reflect the real drilling complex incidents and accidents, make the accurate diagnosis and treatment to the accidents, play an important role in the reduction of accident handling time and the accelerate of the drilling process speed. The system is the combination of artificial intelligence and computer technology. It is the free employed drilling accident experts for the on-site drilling crew, which can provide a strong support to the drilling technical personnel.In the domestic, offshore oil and gas has proposed to use Monte Carlo simulation to estimate risk, but only taking consideration of risk factor of objective conditions, as weather storm, change of market, in addition, there is still no supportive and effective conducting plans. So, there has not existed integral software to evaluate and analyze the drilling risks so far.In the foreign, many conducting risk evaluation and management method have been worked out, like H.Tom of Landmark takes advantage of existing experience to propose "Learning curve analysis method" to decrease30%-40%of corresponding drilling cost; S.K.Peterson in Richardson uses Monte Carlo simulation to calculate the possibility distribution to reflect exploration risk; Heiberger supports good risk policy decision method through integrated technology and commercial risk simulation analysis, combining with reservoir work, drilling work and NPV, which obtain a large mount of commercial profit; BPAmocoNorge UA uses "(before)plan-drilling-plan" circulatory system to get obvious effects in two years exploration and drilling in five oilfields. These methods all apply risk evaluation to estimate drilling accidents, which improve drilling plans and management level and reduce drilling risk. However, the foreign just propose practicable method to manage drilling information and evaluate risk, the application of drilling risk evaluation is rare.The thesis simulates to use Analytic Hierarchy Process to analyze the risk factors of to-be-drilled wells, carrying out prediction before drilling, working out appropriate construction design program to evade complex situations and accidents efficiently along the process of drilling and lower risk level.