The Research Of Optimized Drilling Expert System On Shale Gas

In Fuling block, due to the lack of scientific evaluation system about the drilling technology integration and the corresponding comprehensive benefit and speed, that has been seriously restrict and affect the shale gas drilling construction overall forecast and evaluation. Accordingly, this paper focused on studying a scientific evaluation system that’s used to evaluate the drilling technology integration patterns in the Fuling block, it will be with very important practical significance in solving a series of engineering problems of the Fuling block shale gas drilling. Combined computer technology with actual situation on site, then developing a comprehensive evaluation expert system. Based on the drilling evaluation system, using the field data reasonably, evaluating the application effect and economic benefit of the fuling area optimized drilling technology integration system, finally, finding out the most optimal drilling technology base application pattern that is suitable to Fuling block.This article begins with a simply overview of the main to the emergence and development of expert system, along with the present situation of drilling expert system at home and abroad; Then, made some introduction of the function, structure and classification about the expert system.In the part of the theory researching in expert system, it focused on the drilling technical economic evaluation, some other function for the system is the auxiliary part.The evaluation objects can be divided into two categories:One is about the evaluation of technology (the drilling technology of upper section, the conventional and composite drilling technology of the vertical section); One is about the evaluation of the tools (the bit’s type in directional drilling and the directional tools). The evaluation of technology mainly included gas drilling in the upper section (guide eyes, first spud, second spud), water drilling in the upper section and the low density mud drilling in the central section, besides the conventional roller bit drilling technology、the composite roller bit drilling technology and the composite PDC bit drilling technology in vertical section. The evaluation of the tools mainly included the directional drill bit (roller bit directional drilling, PDC bit directional drilling PDC bit) and the directional tool (conventional steering drilling, hydraulic oscillator+conventional steering drilling, rotary steering drilling).About the evaluation of technology, this paper uses the radar map to do the comprehensive qualitative and quantitative analysis. In the evaluation process, the main work includes:(1)Determined the component of the unit footage cost of shale gas optimized drilling in Fuling block:①day fee of drilling machine;②mud cost;③it+screw+down hole tools (shock absorber, while drilling jar, etc.);④cost of air drilling; the additional cost increased by dealing with down hole accidents (such as fishing tool cost, special operations such as explosion string or test card point charge);⑥the directional technical services; ⑦the cost of top drive.(2)Determined the comprehensive analysis indicators:unit footage cost, footage, construction period, the average rate of penetration, cost of bit.(3)The qualitative evaluation process: ①processing all the basic data with standardization method.②processing the basic indicators of the basic index vector with nonlinear transformation. ③calculating data, drawing radar map, giving qualitative analysis.(4)The quantitative evaluation process:①extracting feature vector of evaluation objects;②construct the evaluation vector and evaluation function;③calculating the comprehensive level of evaluation objects, and then evaluating the comprehensive level of evaluation objects and the balanced development of various indicators.About the evaluation of tools, this paper adopts the fuzzy comprehensive evaluation combined with hierarchy analysis method to evaluate, represented by bit evaluation, in the process, the main work includes:(1)Determined five evaluation factors in the process of fuzzy comprehensive evaluation:rate of penetration, bit footage, the bit’s price, well depth, and the new degree of bit.(2)Determined the membership function model of the evaluation indexes:①ate of penetration belong to the positive correlation with the evaluation result; the membership function model of rate of penetration index is the up half trapezoid distribution.②bit footage belong to the positive correlation with the evaluation result; the membership function model of rate of well depth index is the up half trapezoid distribution, ③bit price belong to the negative correlation with the evaluation result; the membership function model of drill bit price index is the down half trapezoid distribution④well depth belong to the positive correlation with the evaluation result; the membership function model of well depth index is the up half trapezoid distribution. ⑤the membership function model of the new degree of bit is determined by the method of fuzzy set operation, its value is mainly based on the greater value of bit teeth and bearing wear.(3)determined the weight of each evaluation factors by the analytic hierarchy process method:(Dbuilding the corresponding hierarchy model of evaluation system, dividing the hierarchy of the evaluation factors;②building the evaluation factor judgment matrix that is based on the scores of the mutual degree of important between each factors given by domain experts respectively;③examining the consistency of judgement matrix, to ensure reasonability of weight vector which request;④solving the judgement matrix of the largest eigenvalues and corresponding eigenvectors, namely, the weight vector of the evaluation factors.In the aspect of software, combined with more than 50 shale gas drilling well history data in Fuling block, systemized the related important information, storaged the key well history data into the database, established the table library about the basic information, formation drilling depth, lithology, lost circulation, fault and complex accident, drilling fluid system and density, assembly, drilling, screw, caliper, drilling time and well deviation data, as well as the system essential user information and log data table library, etc. Completed the construction of function modules about users management module (users information, the role of authority, unit information, personal information); old well management module (well basic information, economic evaluation); the new well management module (new well basic information, new well data’s entry); fault management module (list of accident, accident summary); knowledge management module (technology management, document management); system module(absystem, system help) preliminary.