Abstract
The maturing Middle Eastern oil fields with natural aquifer support or water injection can pose a challenging produced water handling and disposal issues. The increased water-oil ratio also presents productivity problems: many wells will die prematurely due to increased water holdup. The produced water management cost @US$ 0.50—1.00 per barrel involving millions of barrels of water (even at a modest WOR of 50% from current 30–35%) will be in billions due to the high daily oil production rate envisaged. In this paper, we focus on various aspects of downhole oil-water separation, which we believe will lessen the cost significantly. The downhole water separation technology developed and applied in the western hemisphere cannot be directly applied here because of the orders of magnitude higher production rates per well.
Lacking a production flow-loop facility in the region with full-scale production equipment, we use an industry-standard commercial computational fluid dynamics (CFD) simulation tool to investigate inline oil and water separation characteristics under downhole conditions. Specifically, we investigate the startling sensitivity of well inclination in the 80–100 degrees range. We show that it is crucial to control the well inclination within a tight regime to achieve effective and manageable liquids separation in near horizontal wells. We also show that the liquids phase separation in these wells are sensitive to the gross liquids flow rate.
The CFD simulation study reported in this paper will lead to new technology development that can be used to achieve more effective well completion design in near horizontal wells drilled specifically to obtain downhole oil-water separation. The success of such innovative oil-water separation will save many producing wells from dying prematurely and save millions of dollars in produced water handling and disposal.
