SPE 65177 Oil Field Development Optimisation via Layer Integration

Ponomarenko, E.M.; Eremin, N.A.

Авторы: Ponomarenko E.M., Eremin N.A.
Сборник: SPE European Petroleum Conference held in Parls, France, 24-25 October 2000
Глава в коллективной монографии
Год издания: 2000
Место издания: SPE Parls, France
Первая страница: 058
Аннотация: SPE-65177 Oil Field Development Optimisation via Layer Integration Nicholay A. Eremin/Oil & Gas Research Ins., Yevgeniya M. Ponomarenko/ Oil & Gas Research Ins. Abstract The considered exploited oil field is a layered field and thus characterized by a high extent of heterogeneity of its reservoir constitution and fluid properties. Our task is to optimize its development using an original method. Selection of exploitation plays is an important part of oil field development projects. Our method of the layer similarity estimation allows to optimally integrate the layers into the exploitation plays. The main purpose of our method is to optimize the well performance and to decrease the technological risk. The technique of exploitation play selection is based on multicriterial decision-making approach and fuzzy set theory. The technique under consideration solves several tasks. One of them is the formation and structuring of a set of characteristics influencing the selection of exploitation plays (geological, technological, technical, and ecological ones). The other is the development of a mathematical procedure for layer comparison. introduction To develop a layered oil field it is necessary to integrate the layers into exploitation plays. At the beginning let's determine what the exploitation play is. Exploitation play (EP) is defined as one or several productive layers of a field, which are allocated according to the geologic-technical conditions and economical reasons for joint development by one well system . Incorporation of several layers in one object seems economically efficient, because such an association requires less number of wells for development of a field as a whole. However, the large number of layers in one play can result in less efficient field development2. Some of oil fields nowadays are layered fields, characterized by high extent of heterogeneity of their reservoir constitution and fluid properties. In addition, at the early stages of development the layer data are uncertain and insufficient. The development of layered deposits is influenced by several negative factors, such as the increasing of the product watercontent; the non-uniform oil recovery; the decreasing of current and final oil recovery of each layer and the whole field. These negative factors are caused mostly by combination of the different layers in one exploitation play. The basic parameters of further development depend on the quality of play selection. Uniting the layers with close characteristics into one exploitation play allows significantly reduce the technological risk and smooth the impact of adverse factors. Our method allows to integrate the layers into exploitation plays on the basis of their similarity. Therefore the task of layers similarity estimation is quite urgent. Main Definitions of Fuzzy Set Theory Our method uses the Fuzzy Set Theory for the linguistic description of parameters and for the construction of the belonging functions. Linguistic variable is one of the notions of the Fuzzy Sets Theory3'5. Its basic difference from usual variable is that its values are not numeric, but words or word combinations. For example, porosity = {high, middle, low} where high, middle, low - are term-sets. The belonging function is a term of the Fuzzy Set Theory, which deals with partial belonging to a set3"5. In the traditional logic, on the contrary, a member can either belong, or not belong to the set. According to the Fuzzy Set Theory, the transition of an object from its complete belonging to the set to its complete non-belonging occurs not abruptly but gradually. Belonging degree of an element to the set is a number from the [0,1] interval. Description and Application of Methodology The principles of the reasonable selection of exploitation plays may be specified as follows: - similarity of layers and fluids on the basis of geological parameters - possibility of regulating and controlling the development of each layer included in the exploitation play - stability of oil-water and gas-oil contacts in the exploitation play. Selection of the exploitation play is aimed to achieve the following results: - small number of returnable layers, which reduces the lead time and increases the efficiency of capital investment - most efficient oil and gas recovery from exploitation plays - maximum economic efficiency - the best quality of commercial products • minimising environmental damages. To achieve the above-stated aims, it is necessary first to determine how the layers are to be integrated into the exploitation play. According to our method, the best result is achieved when the layers combining the exploitation play are most similar. This leads to decreasing the influence of negative factors on the development process. The method includes the following steps: 1) linguistic description of the parameters used for the exploitation plays selection 2) creation of the belonging function ^structuring of the layer comparison rules ^estimation of layer similarity along the section and the area of oil field. It should be stressed that the layers similarity estimation uses parameter ratios such as "porosity ratio", "resource ratio", etc. rather than parameters. The ratio of parameters is not only dimensionless. but also more informative, because it shows how much one layer differs from another considering this parameter. The next stage is the construction of the belonging functions. For the majority of our linguistic variables the belonging functions to term-sets "very close layers", "close layers", and "far layers" are constructed on the basis of the statistical information on 200 reservoirs of Russia (Volga-Ural, Timano-Pechora and other provinces) (Table 1). The examples of the belonging functions ("porosity ratio", "permeability ratio", "oil saturation ratio" and "net thickness ratio") are represented in Fig. 1. On the third stage the system of layer comparison rules is proposed (Table 2). This step is one of the most important in approach. When the reservoir engineers try to solve some s. they rely on certain knowledge subdivided on skills and rules. These skills for the considered task consist of well-known assumptions and conclusions. In turn, the engineers construct the rules on the basis of certain logical positions. The last stage of our approach is the actual comparison of layers using a number of parameters. At the beginning, the "basic layer" is selected from the whole layer set according to the size of its resource (30 or more per cent of ultimate reserves). Further comparison is conducted in respect to this layer. If there is no such a layer, then comparison of layer pairs is carried out In any case, this is conducted as follows: first, the parameter ratio is determined; second, the degree of belonging to the term-sets is estimated; third, the minimum-operator (pessimistic estimation) is defined. This operator determines the layer similarity by a number of parameters. The closest layers are united in exploitation play. The layer comparison procedure consists of two parts. In the first part the layers are compared by their average parameters (along the section), while in the second part - by the well parameters (on the area of oil field). The software package is created for these two parts of the layer similarity estimation. The first part of the estimation is resulted in constructing the similarity charts (Fig. 2). The second part of tlte estimation is resulted in constructing the maps of successfulness on the area of allocated plays (Fig. 3) This work serves as a basis for the selection of an exploitation play both for the association of layers into exploitation play (at the early stage of oil field development) and for splitting the exploitation play (at the later stages of oil field development). Results We have shown that field performance depends on how successfully several layers with similar properties can be integrated into one exploitation play. Our method has been implemented during the development of the Volga-Ural field. This field contains five large layers that are characterised by high heterogeneity of their reservoir constitution and fluid properties. To achieve high technical and economic results of Volga-Ural field development, the layers with similar geologic-physical characteristics have been united in exploitation plays. As a result, the efficiency of field development process has increased. Conclusions The methodology of the layer similarity estimation allows to avoid the inaccuracy and incompleteness of geological information and to solve the problem of the selection of exploitation plays. This improves the quality and reliability of design decisions and results in optimization of the layered oil field development Acknowledgments We thank Yudovina Elena for valuable discussions and help. References 1. Ivanova, M.M. et al.: Oil & gas geology and geological basis of oil and gasfield development, Moscow, Nedra (1985) 422. 2. Kanalin, V.G., Dementiev L.F.: The method and practice of the selection of exploitation objects on layered oil fields Moscow, Nedra (1982) 224. 3. Saaty, T.L.: "Measuring the fozziness of sets" J. cybernetics. (1974) Vol. 4. 53-61. 4. Zadeh, L.A.: The concept of linguistic variable and its application to approximate reasoning, N.Y.: Elsevier (1973). 5. Borisov, A.N. et al.: Models of the decisions making on the basis of linguistic variable. Riga: Zinatie (1982) 256. 6. Heider, F.: "Attitudes and cognitive organisation" J. Phychol. (1946) Vol. 21. 7. Gudman, S.E., Hidetniem, S.T.: The introduction to development and analysis of algorithms Moscow, Mir (1981)
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SPE 65177 Oil Field Development Optimisation via Layer Integrationстатья

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