Research On Induction Logging Interpretation Method In Horizontal Well Of Shale And Sand Profile Formations

At home and abroad, the high-angle and horizontal(HA/HZ) well technology has been widely applied to different types of reservoir's exploration and development, the horizontal well logging technology (in particular, logging while drilling(LWD) technology) is also been increasingly improved. With the continuous exploration and development of Daqing Oil field, high angle and horizontal well have been widely used in Daqing Oil Field. It is very difficult to exploit the upper part of middle and thick reservoir which is not flooded by using vertical well in La-Sa-Xing Oil Field,at the same time it is very expensive to exploit the low porosity and permeability formation by using the vertical well in the external region of Daqing Oil Field. It can expand the production area, increase reservoir production capacity, and enhance reservoir recovery by using the horizontal well's technology. It has already become a major means to tap the potential of non-homogeneous reservoir.In recent years, the number of horizontal wells ascends year by year in Daqing Oil Field. The horizontal well technology will become an important technique which can ensure stable production in Daqing Oil Field. Daqing Oilfield has introduced LWD, LWD must be measured while drilling horizontal well in order to facilitate geosteering. In the oil-based mud conditions, LWD can mainly measure engineering parameters, GR and the electromagnetic logging. They can not fully satisfy the requirements of formation evaluation. Therefore, the conventional logging can be measured in the horizontal well by using pipe transmission. The induction logging is the mainly electrical logging. At present, the horizontal well logging's interpretation can only follow the vertical well's interpretation, because it does not have its corresponding method. As the horizontal well's borehole is different from the vertical well's borehole at the spatial location of the formation, the borehole and layer interface is basically horizontal. At the same time, the anisotropy state between the formation and logging apparatus is different from the vertical well's, the well logging's response is also different. It is very difficult to divide the layer's interface and recognize the fluid properties by using vertical well logging's interpretation. At present, it focuses on three aspects in the horizontal well logging's data processing and interpretation: At first, the horizontal well logging instrument's response can be studied by numerical simulation technology. The various factors of the resistivity logging (Lateral, induction and electromagnetic logging) instrument response can be analyzed. The interpretation chart can be manufactured by using the factor's analysis result. At the second, the anisotropic experimental research mainly focuses on the rock anisotropy measurements and the anisotropic calibration of logging data. The third is the horizontal well logging's data processing and interpretation software development.It is the structural reservoir in La-Sa-Xing Oil Field of Daqing Placanticline. The facies are the large river, delta. The oil field mainly develops Saertu, Putaohua and Gaotaizi reservoirs. Their thickness reduce gradually from north to south. The lithology is sand and shale. The property of the reservoir decreases from north to south. It is a large-high oil field of middle-high abundance. The main type is the lithology and stuecture's reservoir in the external region of Daqing Oil Field. The type of reservoir is complex. The types of sediment and strata are excessive. It is the complex lithology, manifold diagenesis, low-middle porosity and permeability, low seepage's ability and low abundance's medium-large–sized oil field.The value of induction's resistivity is 3.5-4.5Ωm at the shale of La-Sa-Xing Oil Field. The value is 7.0-110.0Ωm in the reservoir. But it is 10.0-25.0Ωm in the thin formation. The value is less 30.0Ωm in the external region of Daqing Oil Field. Some reservoir's value are only 5.0Ωm. The value is not credible if it is greater than 110Ωm, because the principle of induction logging restricts. If the value is very high, it can refer to the dual-lateral's value. Therefore, the value of induction's resistivity in the shale is 3.5-4.5Ωm,the value of reservoir is between 5.0 and 110Ωm.The main target of HZ wells is the upper part of middle-thick reservoir at La-Sa-Xing Oil Field and the thin reservoir at external region in Daqing Oil Field. According to the charateristics of the reservoir, the formation's model not only covers the actual reservoir, but also simplifies the conditions to outstand various factors. It is the principium to build the formation's model. Through carefully analyzing the formation's condition in HZ well, it builds two kinds of models for the three-dimensional numerical simulations of induction logging. One is the HZ well's model, the other is HA well's model. Usually the two models can cover all of the circumstances in the HA/HZ wells.After 80 years of the 20th century, due to the developing of the HZ well logging's technology and computer, the study on the three dimensional numerical method in the HA/HZ wells arouses widespread attention. It develops rapidly. Without considering the condition of borehole, invasion and so on, the fast Fourier - Hankel transform is the most effective method.And it has been used to build the chart. For solving the problem of more complex three-dimensional media, the effective method of solving the numerical solution are the finite difference method and finite element method. As the finite difference method is used in a structured mesh generation method it lacks of flexibility while it simulates the geometric profile of HA well and non-uniform's invasion, it is not easy to achieve in the computer. Therefore, this paper develops the three-dimensional finite element method to simylate three dimensional electromagnetic field of the induction well logging.The finite element method is one kind of mathematical simulation technology which can solve mathematics boundary problems. It has been firstly proposed in 40 years this century .It was gradually applied to solve the electromagnetic problems. The method is widely used to the numerical analysis. It applies to any form of geometric shapes with complex boundary objects, complex boundary conditions and complex media.In the numerical simulation the first is to set instrument and formation parameters, and to establish instrument and formation's model. Secondly it creates three-dimensional finite element geometry( three-dimensional mesh generation), The mesh generation is carried out in cylindrical coordinates. The whole range is divided into tetrahedral. It can be considered instruments, borehole, flushed zone, invaded zone and the undisturbed formation in the radial direction. The well axis is vertical axis. It can consider the thickness of different media. In order to ensure that each tetrahedral geometry doesnot pass throuth other regions. It can use variable metric method to mesh in the radial and vertical axis. Thirdly, according to the mesh generation, it can discrete to the partial differential equations in the electric and magnetic fields on the condition of the time-harmonic. It sets the electromagnetic field's boundary conditions, and gets the finite element equations (ie linear equations) of the discrete electromagnetic field. The conductivity of different elements form the coefficient matrix of linear equations. Finally, the value of resistivity can be obtained by solving the coefficient matrix resistivity value. The most critical issue is the grid mesh and eliminating pseudo-solutions in solving three-dimensional electromagnetic field. The grid mesh affects directly to the stability of solution and computational efficiency. The problem of pseudo-solution affects to the corretion of solution. In the mesh generation's process, the variable metric method can reduce the number of calculated units effectively. The tetrahedral element as the basic unit can ensure the stability of the results and flexibility of simulating special electrical boundary's media. With solving three-dimensional electromagnetic field, this paper uses the differential method to eliminate the pseudo-solution.In order to verify the accuracy of numerical simulation software, the three-dimensional simulating results compare with the results in full uniform formation, the results by using three-dimensional software to calculate the two-dimensional stratigraphic model and the Schlumberger's chart. Through the data and analysis of error, numerical simulation's accuracy can satisfy to build the chart.The main factors of horizontal well induction logging are the reservoir's thickness and shale by using three-dimensional numerical simulation. The practical experience can vertify the result too. Therefore, when doing the factor's correction of HZ well's induction logging, the key charts are the reservoir's thickness and the shale. It can ignore the mud invasion, instrument bias and so on.Well logging data processing and interpretation software about the HZ well logging achieves result's visualization and output by using a visual programming language, interactive capability. The software can output the trajectory projection, well three-dimensional space's trajectory, logging vertical depth's projection, reservoir evaluation result's map of vertical axis profiles well, well trajectory comparison's map of the HZ well and adjacent wells, and the evaluation's map on relation between the hole and reservoir. There are six maps and two tables. One table is the borehole's factors, the other is the interpretation's result.By using the method above said, it is applied in the La-Sa-Xing oil field and the external region of Daqing Oil Field. And it got a good geological effect. It plays a supporting role as keep 40 millions'yield for Daqing Oil Field.In this paper, it focuses on the characteristic of the thick reservoir's upper part and the low porosity and permeability formation in Daqing Oil Field. It studies the induction logging instrument's response under the condition of the horizontal well by using three-dimensional numerical simulation technology. It analyzes the influence factors of the induction logging in detail and makes the corresponding correction charts about the main factors. In this paper, according to the horizontal well logging's interpretation procedure, it establishes the horizontal well logging's data processing and interpretation methods of sand-shale reservoir in Daqing Oil Field. And it develops a set of the corresponding software. By solving the problem, it can strengthen the understanding of the relationship between the horizontal well logging interpretation and reservoir. It can improve the horizontal well logging interpretation's tally. It can satisfy the need of horizontal well's production.The main task of the horizontal well logging's interpretation is to carry out the formation evaluation and describe the relationship between the well's trajectory and the reservoir. Through the development of three-dimensional numerical simulation software, it can establish the main influence factors'correction charts of the main factors under the conditions of the horizontal well. The aim is to reflect the layer's true characteristics by using the logging information. By using the study of relationship between the horizontal well's track and the reservoir, it can accurate the understanding of reservoir. In addition, while the domestic logging while drilling technology improves continuously, the LWD data's interpretation and evaluation techniques will be the trend of development in the future.