The Application Of Experiment Design And Response Surface Methodology In The Selection Of Gas Well Completion String

With the further demand of the energy and increasing attention to environmental issues, natural gas was widely paid attention to. The development of Gas engineering technology has become trend of the contemporary world, good gas engineering plan is the key to achieve high and stable oil production and the optimal rational exploitation. Reasonable arrangement of various development methods, which makes the best economic benefit in the oil field development period, has always been the objective of oilfield development workers.Usually, there are three factors needing to consider while selecting gas well tubing size. First, the pressure loss inside the wellbore can’t be too big, keep the wellhead pressure in the long-term process to meet the requirements of the project. Second, it has the strong ability of liquid loading, avoiding wellbore effusion in normal production process, Third, require the flow velocity can’t be too high, in order to prevent the downhole tubing string of erosion damage, if need to revise the reservoir, we must also take into account the requirements of string, comprehensively consider the influence factors of well completion tubing selection, make use of design of experimental method (design of experiment, DOE) to realize the completion string of choice. In order to determine the critical stop spraying standards and dewatering gas recovery feasibility analysis, using the inflow and outflow performance combining the relative permeability curve to find out the relationship between water yield under different water saturations and bottom-hole flowing pressure, to get the critical stop spraying standard. Combined with reservoir engineering method, to evaluate the gas well dewatering gas recovery feasibility. Natural gas hydrate formation forecast,which is to judge whether hydrate formation,is by making use of engraving method bono maleev method and thermodynamics method combined with wellbore temperature and pressure coupling calculating.In order to study lots of oilfield optimization problems, oil engineers introduced a series of optimization method (large system theory, system engineering, optimal control theory, modern decision analysis,fuzzy mathematics,the gray system theory, etc. These methods, in solving optimization problem, especially the whole optimization problem, not only consider the geological properties,permeability and development technology factors, but also combine with the various oil field index requirements of the people, addtionly, considering immediate and long-term goal of oil field. Optimization method in solving problems is far more than the traditional methods and the conventional ways, first, according to the system problem to solve, to do the detailed system analysis and determine the optimal objective to set the objective function, and find out the interaction relationship between the parts of the system and the levels, set up the quantitative model and simulation process. According to the requirements of the scene, transfer the complex problem into a mathematical model, but without any increase in investment conditions, using the computer simulation, to solve the optimal problems, and find out the optimal plan.which has an important significance to reduce the energy consumption, improve work efficiency, and improve the economic benefit.Experimental design is an important branch of the statistics, the main research is how to formulate the appropriate test plan and how to test effective data. a variety of Experimental design ways, early method s:area group design, Latin square design; But most common use in current production and scientific research:orthogonal experiment design,regression design, parameter design, uniform design, mixing design, etc. currently, the design of experiments has been widely applied in various fields of engineering.The response surface method is the combination of mathematics method and statistical method, is to be used to model and analyze the points of interest which is inflected by the response variables, and the ultimate aim is to optimize the response value. Because the RSM simulation process considered as a indestructible black box that is easily and randomly to combine the simulation and certainty simulation problems, so which gets a very wide range of applications. For recent ten years, as the development and application of statistics in various areas, the response surface method is further to expand the application field, and more and more scientific workers are interested in the response surface method, The application fields of response surface methods no longer is limited to chemical industry, medical and biological pharmacy areas which have been applied widely. At the same time, food, engineering, ecology, etc. which are also involved the application of response surface method.The response surface is actually to explicit the unknown relationship between responses and the independent variables. of course, the explicit relationship is approximating the range of independent variable changes, generally, when mentioned the response surface analysis which means match the polynomial formation of the responses and the independent variables based on the experiment design, so which is divided into the first order,second order,three order or even higher order number.In this paper, realizing the optimization design of tubing size requirements which affect the tubing anti-erosion speed and acid stimulations, to make sure the requirements in the development of design scheme will be more scientific and reasonable, in this paper,using the multivariate linear regression method, three steps to solve practical problems.The first step, make sure that the objective function yThe second step, determine the decision variables through the reservoir engineering theory method, determine various variables and the constraint rangeThe third step, choose the appropriate model, with the right model of the sample data analysis and matching, minimize the model vibration, enhance the adaptability of the data to the model, diminish the error, improve precision.Through the above steps, establish the oilfield optimization model.objective function:max(y)=f(x1,x2......xk)The traditional design method can only be built on a single index basis analysis, can’t know the influence of interaction factors on the index, Through the smart arrangement of experiment design, we can quaintly analyze the factors and their interactions on the influence degree of the tubing selection. Through the response surface method, make the anti-erosion of the largest gas production different schemes in the form of regression, and concluded the dependent variables that influence on choosing the related parameters, in the aim of anti-erosion tubing diameter as the objective function equation, while combination with the gas engineering related theory research, predict the anti-erosion tubing choice through the calculations of the model equations.This article, considering the tubing choice is affected by various actual situation factors, take a certain oilfield block as an example, introduced the application of experimental design and the response surface method in oil and gas field development scenarios, overcoming the limitations.That the traditional method can not determine the interactions among factors.