The Reservoir Evaluation With Well Logging Data On Carbonate Formation In H Oilfield

The carbonate reservoirs distribute widely across the world; and people are paid much attention on it due to its high productivity and reserves. Because the lithology of carbonate reservoirs is so complex with heavy non-homogeneity, it is very hard to be evaluated. The well log is as an important technology to exploration and development activities, so it plays the important role in the carbonate reservoir evaluation. In this paper, through the study of carbonate reservoirs with logging data in oversea oilfield, it is hoped to establish a set of suitable carbonate reservoir evaluation methods, and the methods can be used for reference to evaluate carbonate reservoirs in other oilfield.H oilfield is a reservoir with gas cap and basal water, and the target formation is tertiary carbonate reservoir. The purpose is to establish a set of the evaluation method of proper carbonate reservoir by using logging data, which is reservoir parameter determination, oil gas contact and oil water contact in order to identify the fluid property, and set up the reservoir classification criterion and interpretation standard. Through the collection and arrangement of the development data, including logging data, core data, mud logging data and well testing data, the difficulties are as the follow: 1. the lithology is very complex, and the formation is composed of limestone, calcareous dolomite, dolomite and anhydrite; 2. the reservoirs are heavy non-homogeneous, and the reservoir parameter determination is difficult due to fracture existence; 3. OGC and OWC are hard to identify due to long term development; 4. there are no suitable reservoir interpretation and classification criterion. According to these characteristics, the reservoir evaluation in H oilfield has to begin from the core data analysis firstly in order to obtain the useful geological information, including lithology, petrophysical property, electrical property and the reservoir style, etc. And then the response characteristics of these different geological properties are analysed, finally, the reservoir evaluation is carried out by using logging data combination with mud logging data, well testing data, etc. The study clue in this paper is that the core data in some key wells have been used to carry out the petrophysics analysis, and obtained the useful geological information on target formation. After that, four important factors which affect the reservoir quality were obtained, which are the dolomitization degree, shale content, the pore throat size and fracture development. Then using the logging data combination with the petrophysics result of the core data analysis to obtain the logging data response characteristics of the'four properties', finally the reservoir evaluation are researched with logging data combine with mud logging data and well testing data in order to solve the geological issues. The core resistivity analysis shows that the cement index and saturation index are variable with the different reservoir quality. Therefore, the variable cement index and saturation index have to been adopted to calculate the water saturation in the different area. In order to establish a suitable method of reservoir classification, the porosity cut-off has to been determined firstly with core data and mud logging data by using cross plot, then combine with capillary data, relative permeability data and imaging log data to establish the reservoir classification criterion. By doing so, through the relative permeability data analysis, the different interpretation standards were established according to different reservoir quality. The highlights in this paper are that acoustic impedance and corrosion factor have been used to determine OGC and OWC, which are hard to identify.Through the carbonate reservoir study in H oilfield, the suitable reservoir evaluation methods have been established, and provided the useful and helpful reference data for the further development activity. These methods can be used for reference to evaluate carbonate reservoirs in other oilfield.