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ISBN 978-952-5726-09-1 (Print) Proceedings of the Second International Symposium on Networking and Network Security (ISNNS ’10) Jinggangshan, P. R. China, 2-4, April. 2010, pp. 170-173 Comprehensive Evaluation of Drilling Risk Based on Unascertained Measurement Jun'e Liu 1 , and Rong Wang 2 1 Information school ,Beijing Wuzi University,Beijing 101149, China; Email: zl-je@163.com 2 School of Economy and Management,Hebei University of Engineering, Handan 056038, China Email: wangrong246437@sohu.com Abstract—Drilling engineering is not only a systematic engineering that involves several workcategories, work procedures,intersectant and continuous operation, but also is a concealed underground engineering. There are uncertain factors in drilling projects, which have the characteristics of high investment and risk. On the basis of the overall analysis of the two factors of geology and engineering, the risk evaluation model of drilling project is established by creating the hierarchy structure of drilling risk and introducing the uncertain measure comprehensive evaluation method. Taking Yanchang Oilfield 21 Well as an example, a comprehensive evaluation is studied and then draw a reliable conclusion. Therefore, unascertained measure evaluation method is applicable, efficient, and necessary to promote safety production, which provides the new way for risk assessment of drilling project.. Index Terms—drilling project, risk evaluation, unascertained measure I. INTRODUCTION Drilling is a covert and underground work, which is full of fuzzinesses, randomness and uncertainty, so it is truely a kind of high-risk work. The object of drilling is the stratum rock, and the goal is the oil and gas exploration. In drilling operation process, the lack of understanding to rock buried deeply in earth crust (objective factor) or technical factor (engineering factor) as well as decision-making fault (human factor) tend to bring about many complex mine situations and even serious downhole accidents that consume effort, money and time and may even lead to the waste of oil and gas resource as well as the abandonment of the mining site. According to analysis of drilling data in recent years, the time of solving complex mine situations and drilling accidents approximately accounts for 5%~8% of the total drilling time. Dealing with complex mine situations caused by geologic agent correctly and avoiding or reducing drilling accidents caused by decision fault have important significance to guarantee safety production, staff health and environmental protection[1]. Therefore, combined with engineering characteristics of drilling, comprehensive evaluation of drilling risks is made on the basis of analysis of single-factor,so as to provide a basis for scientific decision-making. II. RISK RECOGNITION OF DRILLING On the basis of the overall analysis of survey results of local drilling environment; drilling activities prone to accidents; routine management experience; people's behavior, physical condition and environmental factors etc., we carries on the distinction to various risks in a latent state in drilling implementation process. Only identificating drilling risks accurately, knowing types, characteristics and potential hazard of risk incident can we take the necessary steps to guard against. There are a large number of factors that make drilling complex and dangerous, but in summary , of which mainly are two categories---geological factors (the objective conditions), and engineering factors (subjective decision-making) [2] . A. Geological factors In terms of oil and gas drilling projects, the geological factors include rock types and its nature of engineering mechanics , geological structure, formation fluid situation and stratigraphy circumstances and so on. Taking into account the complexity of geological factors and the extent of indicators quantified, geological factor is divided to formation factor and sulfur-containing gases. 1) Formation factor :Drilling is a process of drilling gradually by constantly breaking formation rock. Drilling process and its risk factors closely related to the mechanical properties of rock and formation pressures, which directly influence drilling efficiency and technological measures, particularly the balance between formation pressure and bottom-hole pressure. In oil and gas drilling, we should maintain balance between formation pressure and bottom-hole pressure (static liquid column pressure). Otherwise, many complex situations or accidents such as well-kick, blowout, lost circulation, fracturing formation are likely to happen, so as to make drilling difficult to carry out, and even make borehole abandoned. 2)Sulfur-containing gases : Sulfur-containing gases mainly refers to the hydrogen sulfide gases encountered in the process of drilling. The sources of hydrogen sulfide can be attributed to the following kinds::1sulfate in the stratum produces hydrogen sulfide under hightemperature reduction; 2 decomposition of the sulfurcontaining in oil compounds and resultes in hydrogen sulfide; 3hydrogen sulfide in deep crust migrate and accumulate upwards through cracks; 4decomposition of © 2010 ACADEMY PUBLISHER AP-PROC-CS-10CN006 170
some drilling fluid produces hydrogen sulfide under the action of high temperature. Hydrogen sulfide is a gas of colorless, toxic, strong acid. Hydrogen sulfide gas in low volume fraction has a smell of rotten eggs, the relative density of which is 1.19. Compared with air, it is heavy, and it can dissolve in water. When burning, it accompanied by a blue flame and produces sulfur dioxide gas that is very harmful to the person. The mixture of hydrogen sulfide and air, while mixture gas volume fraction lie the range of 4.3% ~ 45% , form a kind of explosive mixture. Hydrogen sulfide is easy to gather, not easy to drift, often gathering at the bottom of drilling platform or the lower well site. It can react with many metals and can corrode of metal severely. When volume fraction of hydrogen sulfide gas in the air is greater than 10 × 10-6 , people feel discomfort, and when that is more than 20 × 10-6, may cause poisoning. In general, volume fraction of hydrogen sulfide increases with increasing formation depth. The presence of hydrogen sulfide is in two forms, either in the form of hydrogen sulfide gas alone or coexisting with oil and gas; or in the form of dissolving in water and oil. In drilling process, the hazards of hydrogen sulfide can be summed up in four aspects: 1 harm on the human body; 2 corrosion of drilling equipment; 3 contamination of drilling fluid; 4 pollution of the environment[3]. B. Engineering factors Geological factor is the objective reality and can not be changed. If we have better understanding about it and take corresponding countermeasures, we can turn danger into safety, reduce the complexity of drilling, and avoid the accident. Engineering factors is a specific manifestation of subjective factors, that is construction design, technical operations, craft measures and so forth and is suitable for geological factors. It is human factors, modifiable and adjustable. For engineering factors, see Table1. III. COMPREHENSIVE EVALUATION OF DRILLING RISK AND MODEL BUILDING Comprehensive evaluation of drilling risk is that the organization of professionals, based on existing professional experience, evaluation criteria and guidelines , identify possible risks or impacts at predrilling activities, evaluate and analyze scientifically, calculate the probability ,value and consequences of the risk by quantifying risk factors, and thus determine whether the project risk may be accepted. Comprehensive evaluation methods mainly are analytic hierarchy process, decision tree method, monte-carlo method, fuzzy comprehensive evaluation etc. In this paper, unascertained measure evaluation method is adopted for analyzing and processing, and its evaluation results can be quantified accurately. The specific process is as follows: A. Establish hierarchy structure of drilling risk Establish hierarchy structure of risks by risk identification, like Figure1. Target layer denotes the object evaluated. Criterion layer is factor categories that evaluation object contains, that is two elements of drilling risk assessment. Each element is a relatively independent entity, which can be used as an object for study. Index layer is indicators that various factors included. B. Determine the weight of each factor In drilling project, the importance of each evaluation factor is different, therefore we should determine their weighted coefficient according to relationship between primary and secondary to risk effect. In this paper, AHP method is adopted to determine the weight set of evaluation factors, that is to have experienced experts to make a comparison with the importance of two indexes to construct a consensus judgment matrix, then to get the weight value using the group decision-making coordinate method. C. Establishment of unascertained measure evaluation model In comprehensive evaluation of drilling engineering, analyzing and evaluating risk factors of system quantitatively and intuitively is an important part in theory circle. As drilling process involves a lot of uncertain information, use unascertained mathematics dealing with this issue. 1) Single-index measure modle of drilling risk assessment:In Figure1, X indicates object space,then: X =( x 1 , x 2 ), thereinto x 1 , x 2 indicate geological factors and engineering factors respectively. To evaluate the object need to identify m indexes, if x indicates ij measured value of object x with regard to index i I , then j x can be expressed as m dimensional vector: i x i = ( x , x , L , x ) ;then x1 = ( x11, x12, x13) , x2 = ( x21, x22, L , x28) . i1 i2 im 171
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Proceedings The Second Internationa
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Table of Contents Message from the
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Zuming Xiao, Zhan Guo, Bin Tan, and
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Message from the Symposium Chairs T
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Second International Symposium on N
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model that can deal with time serie
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training for the Wushu competition
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information, called weak uncertain
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Student side Student side Student s
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If we define element of student as
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QoS, each frame data is divided int
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for Imaging Two and Three Phase Flo
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A. Profiling&following control algo
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Research and Realization about Conv
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support 10 Mb / s. But ENC28J60 onl
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According to maximum membership deg
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ubber according to the mass ratio o
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Ⅲ. AN IMPROVED DNA ALGORITHM FOR
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Ⅴ.CONCLUSION REMARKS DNA computer
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its first child q 1 on the left, th
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chains can greatly improve efficien
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II. RELATED WORK A. Mobile Service
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special services. SOAP is used to b
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detection methods of DDoS attacks m
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Step4 calculate the new subordinate
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Figure 1. An analysis of the partit
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The preceding three formulas can be
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And the decay speed of buffer seque
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distance of view point. Given that
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Ⅳ. EVALUATION OF BLENDED LEARNING
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symmetric with respect to the origi
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each sample belongs to each categor
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A. Data Preparing To generate our t
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Strong earthquake 0.1< M L
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indirect causes, and the logical re
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egression. Granger causality test i
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B. Evaluation We have evaluated thi
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used as a source and neighboring ce
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Figure 3. Drainage networks generat
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Combinational logic unit failures i
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B. Simulation results and analysis
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in routing table. When search resou
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others through the selective emotio
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such as weather information, techno
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the opening window, a related page
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1) Process context storage areas. I
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V. CONCLUSION In this thesis, sCPU-
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main types of horizontal search env
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Enterprise Portal security provides
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[2] Kumaravel, N., and Kavitha, V.,
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output, so BP network has been wide
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input to the artificial neural netw
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Error 8000 7000 6000 5000 4000 3000
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Architecture (AMBA) a new bus archi
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In this paper, we adopt two Sobel o
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four layers.The far right of the gr
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TABLE II. OPERATIONAL EMPLOYEE TABL
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A. Object-relational Type To audit
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to execution time. Also, DBA would
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Liping Chen .......................
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