Gravity Drainage and Oil Reinfiltration Modeling in Naturally Fractured Reservoir Simulation

2007 ◽  
Author(s):  
Juan Ernesto T. Ladron De Guevara ◽  
Fernando Rodriguez-De La Garza ◽  
Agustin Galindo-Nava
Keyword(s):  
Reservoir Simulation ◽  
Gravity Drainage ◽  
Fractured Reservoir ◽  
Naturally Fractured Reservoir ◽  
Naturally Fractured

Gravity-Drainage and Oil-Reinfiltration Modeling in Naturally Fractured Reservoir Simulation

2009 ◽  
Vol 12 (03) ◽  
pp. 380-389 ◽  
Author(s):  
Juan Ernesto Ladron de Guevara-Torres ◽  
Fernando Rodriguez-de la Garza ◽  
Agustin Galindo-Nava
Keyword(s):  
Reservoir Simulation ◽  
Fractured Reservoirs ◽  
Dual Porosity ◽  
Gravity Drainage ◽  
Fractured Reservoir ◽  
Fluid Exchange ◽  
Production Forecast ◽  
Naturally Fractured ◽  
Matrix Blocks ◽  
Refined Grid

Summary The gravity-drainage and oil-reinfiltration processes that occur in the gas-cap zone of naturally fractured reservoirs (NFRs) are studied through single porosity refined grid simulations. A stack of initially oil-saturated matrix blocks in the presence of connate water surrounded by gas-saturated fractures is considered; gas is provided at the top of the stack at a constant pressure under gravity-capillary dominated flow conditions. An in-house reservoir simulator, SIMPUMA-FRAC, and two other commercial simulators were used to run the numerical experiments; the three simulators gave basically the same results. Gravity-drainage and oil-reinfiltration rates, along with average fluid saturations, were computed in the stack of matrix blocks through time. Pseudofunctions for oil reinfiltration and gravity drainage were developed and considered in a revised formulation of the dual-porosity flow equations used in the fractured reservoir simulation. The modified dual-porosity equations were implemented in SIMPUMA-FRAC (Galindo-Nava 1998; Galindo-Nava et al. 1998), and solutions were verified with good results against those obtained from the equivalent single porosity refined grid simulations. The same simulations--considering gravity drainage and oil reinfiltration processes--were attempted to run in the two other commercial simulators, in their dual-porosity mode and using available options. Results obtained were different among them and significantly different from those obtained from SIMPUMA-FRAC. Introduction One of the most important aspects in the numerical simulation of fractured reservoirs is the description of the processes that occur during the rock-matrix/fracture fluid exchange and the connection with the fractured network. This description was initially done in a simplified manner and therefore incomplete (Gilman and Kazemi 1988; Saidi and Sakthikumar 1993). Experiments and theoretical and numerical studies (Saidi and Sakthikumar 1993; Horie et al. 1998; Tan and Firoozabadi 1990; Coats 1989) have allowed to understand that there are mechanisms and processes, such as oil reinfiltritation or oil imbibition and capillary continuity between matrix blocks, that were not taken into account with sufficient detail in the original dual-porosity formulations to model them properly and that modify significantly the oil-production forecast and the ultimate recovery in an NFR. The main idea of this paper is to study in further detail the oil reinfiltration process that occurs in the gas invaded zone (gas cap zone) in an NFR and to evaluate its modeling to implement it in a dual-porosity numerical simulator.

Modeling Challenges for Cold Gas Oil Gravity Drainage cGOGD Development of a Naturally Fractured Reservoir and Lessons Learnt –A Case Study, North Oman Oil Field

2021 ◽  
Author(s):  
Chaitanya Behera ◽  
Majda Balushi ◽  
Badar Al Said ◽  
Jeppe Gavholt ◽  
Loic Bazzalgette ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Gas Injection ◽  
Field Performance ◽  
Gravity Drainage ◽  
Gas Oil ◽  
Fractured Reservoir ◽  
Naturally Fractured Reservoir ◽  
Scenario Modeling ◽  
Naturally Fractured ◽  
Cold Gas

Abstract Global experience in cold Gas Oil Gravity Drainage (cGOGD) recovery with crestal gas injection of infield produced gas is very limited, but is a proven economic recovery method for fractured carbonate reservoirs in North Oman. Despite decades of research in nature of fluid flow in fracture-matrix media and application of sophisticated tools in building fracture model of a naturally fractured reservoir (NFR) reliable prediction of the GOGD production performance often proved elusive. Characterization of fracture networks and modeling of matrix-fracture transfer function, gravity induced fluid flow in heterogeneous matrix media especially in case of capillary discontinuity due to tight interbedded matrix and capillary pressure hysteresis are the key challenges for reservoir modeller. Re-infiltration of oil into lower matrix blocks, matrix permeability, fracture density and spacing, wettability and reservoir fluid properties have significant impact on the well and field performance. The risk posed due to undermining the key modeling parameters have huge implication on facility design, subsurface concept and value of the project. The challenges in upscaling the fracture properties in a range of grid scale, experimental design for history matching and uncertainty analysis, understanding the oil rim development in leached zone and numerical options are some of the key aspects which have been illustrated in this paper. The field being on primary production since 1985, showed poor recovery and high water cut. Multi-episodic tectonic events resulted in variable fracture intensity and fracture permeability anisotropy. This study investigated the effects of the parameters on cGOGD recovery process, operating strategy (e.g., gas injection rate and liquid offtake) and on the overall field performance. The development decisions are not simply relied upon the dynamic simulator results, but an integrated understanding from comprehensive analytical calculations for multiple recovery mechanism such as fluid expansion, fracture oil displacement, gravity drainage from background matrix and leached zone and analogue field GOGD performance were taken into consideration. The subsurface development decisions such as producer location with respect to faults and lineament, well pattern & spacing, producer depth, gas injector locations, gas injection scenarios, aquifer pump-out wells and maximum off-take rate were analyzed and optimum decision could be taken from multi-scenario modeling studies. The GOGD development could increase the field recovery up to ~9% at low UTC and positive NPV. A pragmatic and integrated modeling workflow with multi-scenario modeling approach was pursued to address the development risk which facilitated the field to be economically developed. The key modeling challenges have been highlighted for GOGD modeling process with gas recycling option of development which can be replicated in similar fields in PDO.

Convection and Dispersion in a Naturally Fractured Reservoir

2004 ◽  
Vol 7 (4) ◽  
pp. 303-316 ◽  
Author(s):  
E. Luna ◽  
A. Medina ◽  
C. Perez-Rosales ◽  
C. Trevino
Keyword(s):  
Fractured Reservoir ◽  
Naturally Fractured Reservoir ◽  
Naturally Fractured
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