Optimal control policies for carbon dioxide miscible flooding enhanced oil recovery

Thesis/Dissertation · Wed Jan 01 00:00:00 EST 1986

OSTI ID:7175762

Methos, G J

Optimal control theory of distributed parameter systems has been used to develop improved operational strategies for carbon dioxide miscible flooding. The optimization criterion was to maximize the net profitability of the CO/sub 2/ flood. A two-dimensional, three-phase, modified black-oil model was used to describe miscible displacement of oil. Calculus of variations was applied to find control functions that provide extreme for an objective functional which related injection costs and production revenue. Lagrange multipliers, or costate variables, were used to ensure that the constraints given by the equations of the simulation model were satisfied. Control functions computed were the carbon dioxide and water injection policies and the production wellbore pressure history. In order to avoid difficulties in obtaining a stable numerical scheme for the costate equation, a discrete formulation of the optimal control problem was developed. A steepest decent gradient search method was used to find the optimal control law. Starting functions for the algorithm described currently used strategies: a large slug of CO/sub 2/ followed by drive water; carbon dioxide injected simultaneously with water; and injection of small slugs of CO/sub 2/ alternately with slugs of water. Improvements in the cost functional from the starting functions ranged from four to eleven percent. While the optimal control law found was highly dependent upon the starting functions used to initiate the algorithm, the shape of the optimal control law was found to be unique, as was the optimal total volume of carbon dioxide injected and the optimal value of the cost functional.

• Research Organization: Colorado Univ., Boulder (USA)
• OSTI ID: 7175762
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
CARBON DIOXIDE INJECTION
MATHEMATICAL MODELS
PROCESS CONTROL
OIL WELLS
WATERFLOODING
ALGORITHMS
ENHANCED RECOVERY
OPTIMIZATION
PETROLEUM
PROFITS
CONTROL
ENERGY SOURCES
FLUID INJECTION
FOSSIL FUELS
FUELS
MATHEMATICAL LOGIC
MISCIBLE-PHASE DISPLACEMENT
RECOVERY
WELLS
020300* - Petroleum- Drilling & Production