#TITLE_ALTERNATIVE#

• Main Author: ALAWIYAH, SUSANTI
• Format: Dissertations
• Language: Indonesia
• Subjects: Ilmu kebumian
• Online Access: https://digilib.itb.ac.id/gdl/view/13129
• Institution: Institut Teknologi Bandung

The two important aspects in EOR (Enhanced Oil Recovery) to establish of sweep efficiency in the fluid injection process are monitoring and simulating behaviors of the reservoir fluid movement. The behaviors are due to injection and production activities. To obtain description of the reservoir fluid movement, indirect monitoring technology, such as time-lapse microgravity is an alternative solution.<p> So far applications of monitoring time-lapse microgravity method have been based on parameter changes of fluid density and apparent saturation. Both parameters are calculated from gravity anomaly data. During a period of microgravity measurements, the parameter changes indicate two pinpoints. Firstly is increasing or decreasing fluid mass and secondly is replacing reservoir pore fluid. For the case of one layer reservoir, such as carbonate reservoir, the fluid density changes can be estimated using simple method. This is because the gravity response measured on the surface directly represents the fluid density changes in the targeted reservoir. However in a multilayer sandstone reservoir, the estimation of fluid density changes for each layer is determined by the technique used and supported data, such as reservoir physical properties and volume of production and injection fluids from each layer during the period of gravity measurements on the surface.<p> As the novelties of this research, two new techniques have been developed. Firstly, time-lapse microgravity data are used to estimate the fluid density changes in each layer using DSMVD technique (Deconvolution Simulation of Mass Volume Density). This technique combines the deconvolution process of timelapse microgravity anomaly and the simulation technique of fluid movement with supported by injection and production volume data in each layer and also reservoir physical properties. Secondly, fluid density changes resulted from the DSMVD technique are used for simulating a 3-D fluid movement to identify and to predict the pattern and direction of fluid movements in the reservoir in a certain time.<p>To conduct the research, a 3-D fluid movement simulation code has been developed based on an equation of fractional fluid flow for two-phase immiscible fluid. The equation implies a gravity effect that can be quantified by time-lapse microgravity method. Two main outputs of the simulation are fluid density and water saturation values for a certain time after the injection process conducted. In order to test the estimation result from DSMVD and simulation techniques, the code of a 3-D forward gravity modeling has been developed to calculate gravity response on the surface.<p>A case study of the 'SS' oil Field, Central Sumatra, has been conducted to apply the methods in which time-lapse microgravity data were acquired from twice measurements within a six-month period. The 'SS' field is a multilayer sandstone reservoir which consists of A1, A2, B1, B2, B2A, D and S layers. The depth of the reservoir target is approximately 700 m and the average thickness of each layer is 12 m.<p>Monitoring and simulating results show that in general there is decreasing fluid mass (mass deficit) and/or replacing reservoir pore fluid. This phenomenon is caused by fluid volume produced is higher compared with water volume injected. The decreasing reservoir mass (based on the negative gravity anomaly) from the highest to the smallest, occur in B2A, A2, B1, D, B2, S and A1 layers, respectively. The movement of injected fluid in each layer mostly extends to the East and South-East directions. The most significant injected fluid movement occurs in the B2A layer. Based on the pattern, the injection fluid movement is not only controlled by fault structure, having North-South direction, but also controlled by reservoir physical properties especially in the Eastern and Southeastern of the field. In some layers (B1, B2, B2A and D), there are injector wells which are not effective to push oil to the producer wells, especially in the Southern area. To optimize the oil production in the field, it is necessary to put new infill injection wells in the ineffective layers or to the area having low fluid density and water saturation.<p> Based on the research results, it can be implied that monitoring and simulating techniques of time-lapse microgravity need to be conducted to identify the behavior of reservoir relating to the injection and production activities. Using the techniques, it can be obtained the information of fluid density change model representing the decreasing or increasing reservoir fluid mass. The fluid mass change is caused by fluid replacement in pore. Additionally, it can also be inferred and predicted the pattern and direction of fluid movements in a certain time.