Geological modeling and reservoir simulation of Umiat: a large shallow oil accumulation

Geological modeling and reservoir simulation of Umiat: a large shallow oil accumulation

Oraki Kohshour, Iman

Date: 2013-05

Type: Thesisms

Table of Contents: Chapter 1. Introduction -- 1.1. Overview -- 1.2. Objective of the study -- Chapter 2. Background -- 2.1. Field history and location -- 2.2. Previous research -- 2.3. Geologic modeling -- 2.4. Reservoir simulation -- 2.4.1. Incentives for reservoir simulation -- 2.4.2. Designing the simulation model -- 2.5. Horizontal wells -- 2.6. Gas injection -- 2.7. Gas hydrate -- Chapter 3. Geologic modeling, methodologies, and sources of data -- 3.1. Petrophysical property modeling -- 3.2. Permeability anisotropy -- 3.3. Optimal geologic grid design for simulation -- 3.4. Model geometry -- 3.5. Modeling of water saturation: concepts and challenges -- 3.6. Application of petrophysical cut-offs -- 3.7. Monte Carlo estimation of OOIP -- 3.8. Uncertainty parameter ranking by multiple realizations -- Chapter 4. Simulation model: preparation of input data for dynamic model -- 4.1. Rock and fluid data -- 4.1.1. Relative permeabilities to oil and gas -- 4.1.2. Relative permeabilities to oil and water -- 4.1.3. Capillary pressure -- 4.1.4. Fluid properties -- 4.2. Initializing model based on initial reservoir conditions -- 4.3. Design of production and injection wells -- Chapter 5. Results -- 5.1. Oil recovery by gas injection (base case) -- 5.2. Grid size optimization -- 5.3. Parameter optimization -- 5.3.1. Horizontal well length -- 5.3.2. Injection pressure -- 5.4. Sensitivity analysis -- 5.4.1. Permeability anisotropy -- 5.4.2. Relative permeability and end points saturations -- 5.4.3. Producing GOR -- 5.5. Discussion -- Chapter 6. Conclusions and recommendations -- 6.1. Conclusions -- 6.2. Recommendations -- References -- Nomenclature.

Abstract:

Current high oil price and availability of new technologies allow re-evaluation of oil resources previously considered uneconomic. Umiat oil field is one such resource: a unique, shallow (275-1055 feet), low-pressure (200-400 psi) reservoir within the permafrost zone located north of the Arctic Circle, 80 miles west of Trans Alaska Pipeline System (TAPS) with an estimated 1.5 billion barrel of oil-in-place. This thesis presents a reservoir model that incorporates recently identified permeability anisotropy patterns within the Cretaceous Nanushuk sandstone reservoir to evaluate various potential mechanisms such as horizontal wells and immiscible gas injections. The simulation model focuses on the Lower Grandstand which is identified as a better reservoir rock. The reservoir temperature is assumed at 26 OF and gas is injected at the same temperature to maintain equilibrium with the permafrost and prevent any well integrity problems. An optimum horizontal well length of 1500 ft was found and applied for all simulation cases. The simulation results show that with 50 years of lean gas injection, recovery factors for the base case and case of 600 psi injection pressures are 12% and 15%, respectively, keeping all other parameters constant.