The integration of geophysical data, especially 3-D seismic data, with well data can improve the spatial characterization of heterogeneous reservoirs. Various kind of geophysical surveys, such as 3-D seismic, VSP and crosswell seismic, have been carried out for four years at the central part of Amarume oil field in Yamagata prefecture, Japan to characterize the thin sandstone reservoirs. Model-based inversion was confirmed to bring more precise acoustic impedance information of subsurface layers than recursive inversion. So the model-based inversion was applied to three 2-D sections through wells which were selected from the 3-D seismic data volume. We got not only the distribution area of each sand-stone reservoir with lens-shape but also the information of impedance change within the same sand unit. This impedance change can be related to changes of rock properties and physical conditions in the reservoir. The acoustic impedance inversion is being applied to the whole 3-D seismic data. It is expected that geophysical data will play an important role to create models for hetergeneous reservoirs in the future.
Two wells were converted to horizontal completion wells by sidetracking from the existing vertical holes. In Well-A, which has been completed in a low permeable depletion drive reservoir, two horizontal holes were drilled in the adjacent two layers: 767ft in the upper layer and 677ft in the lower layer. As a result, the well production ability has become trippled as compared with that in the vertical completion. Meanwhile, Well-B is located in a high permeable water drive reservoir and has been suffering from high production water-cut due to water coning. A 336ft horizontal hole was drilled in the upper layer after shutting-off the water producing lower layer. As a result, water-free oil production becomes possible and the production rate has increased by four times.
Although quite a few horizontal wells have been drilled in the world, a pressure interpretation using actual pressure data and production profile has been rarely reported. An example of practical pressure interpretation by the Automated Pressure Analysis System developed by authors, together with the prediction results of future production performance by a reservoir model matched with the actual pressure data are presented in this paper. There are several problems for pressure interpretation of a horizontal well. Firstly, the early time pressure data, which is important to estimate KV/KH, are often masked by a, wellbore storage effect. Secondly, when reservoir permeability is low, it takes too long a time for the pressure behavior to reach a pseudo radial flow condition for which the traditional pressure interpretation methods can be applied. Thirdly, due to the rapid change of a flow regime, it is difficult to keep the production rate of a horizontal well stable in the early production stages, as a result, currently available interpretation methods cannot properly anslyze the results. In order to solve the above mentioned problems, we have developed the Automated Pressure Analysis System which can automatically determine four reservoir parameters, i.e. Horizontal Permeability (KH), Vertical-Horizontal Permeability Ratio (KV/KH), Skin Factor (S) and Wellbore Storage Coefficient (CD) from the pressure data, even when the production rate is unstable. On the other hand, pressure matching using a reservoir simulator was conducted and its result was compared with the one by the Automated Pressure Analysis System. The reliability of the Automated Pressure Analysis System was confirmed by comparing the above result independently.
An approach to predict field performance for gas field consisting of lenticular sand has been developed. This paper describes actual distribution of lenticular sands in a gas field and gives an image of these type of fields first. Then, a stochastic model which fully represents a field is introduced. The model is essentially similar with the Monte-Carlo simulation but the concept is different. The procedure to generate the model is presented and discussed. Finally, applying completion and production schemes, production forecast is obtained. Since various production profiles are available for respective development plans, the most appropriate plan is to be selected.
In this paper, application of simulation technology for the evaluation of steamflood pilot test being conducted with a single inverted five spot injection pattern in heavy oil field is described. Numerical thermal reservoir simulators generally take more calculation time than isothermal ones mainly due to strong nonlinearity of the equations caused by fluid viscosity change with tempararure. Therefore, the application to real field performance has been aimed at such a limited area as 1/8 symmetric element of a whole flood pattern. In order to establish the evaluation method for actual reservoir performance, the difficulties mentioned above should be overcome. This paper presents the process and the results of simulation study using 1/8 symmetric model as the first step of the method of evolving a model construction for the simulation of a whole flood pattern. The results obtained here are discussed and proved to be basically reasonable in comparison with actual reservoir performance observed by means of several kinds of monitoring methods. The further steps of enlargement of the model construction will be carried out in the future.
A part of the reservoir in the Kubiki Oil Field has been waterflooded since 1980. Several producers already experienced water breakthrough to this date. In this situation, the project of CO2 flood pilot to this reservoir has been initiated and is in its third year at present. Three investigation wells have been drilled during the last two years in the pilot test area, and the information, such as full series of the state-of-the-art logging data, has been obtained to improve the geological and petrophysical description and to modify our understandings of the reservoir conditions after waterflood. Some conclusions of waterflood evaluation in the pilot area derived from the above mentioned investigations are as follows. • Good vertical sweep efficiency has been achieved. • Irreducible water has been displaced by injection water. • Oil saturation is reaching to residual oil saturation (20-30%) around the target area. • Secondary recovery is about 5% of OOIP while primary recovery was 15%. • Steep pressure gradient exists locally. • Rock facies varies vertically and/or horizontally in relatively small region. The whole above informations will be examined more minutely and merged for the better understanding of the reservoir conditions, which will contribute to design, performance prediction and evaluation of CO2 flood pilot.
Japan National Oil Corporation (JNOC), and the Türkiye Petrolleri Anonim Ortakligi (TPAO) entered into the Basic Agreement in August 1987 on “International Collaborative Research and Development of EOR Technology in The Ikiztepe Field and Vicinity Wells, Turkey”. JNOC has continued the research and development (R & D) of enhanced oil recovery (EOR) technology since early 1970's. Whereas TPAO has many heavy oil fields and found considerable potentials of heavy crude near the Ikiztepe Field and its vicinity area. Both parties endeavour to recover at most heavy crude to improve oil production. As the results of the discussions between the two Parties at the end of Phase 1 feasibility study that is the reservoir evaluation, the EOR evaluation and the pilot test planning of the collaboration. Both parties agree to carry out a feasibility study, and to conduct EOR pilot tests applying both carbon dioxide and steam injection methods for providing basic information on the feasibility of EOR techology application in the Ikiztepe Field and vicinity wells of Turkey.