Autonomous Valve Controls Excess Water, Gas Production To Increase Oil Recovery

Abstract

Increasing sensitivity to oil price fluctuation requires operators to reduce costs of operation. A key component is collaborative management by operators and suppliers to reduce cost over the full life cycle of the operation. Much of the focus is on the equipment-purchasing strategy; nonetheless, effective technology such as an autonomous inflow control valve could also benefit the operating expenditure (OPEX) savings by enhancing oil recovery and reducing processing costs of excessive unwanted water and gas in surface facilities. OPEX comprises labor, chemicals, consumables, infrastructure maintenance, transportation, disposal, and other utilities. Capital expenditure (CAPEX) may also be reduced for long-term projects, which generally comprise infrastructure such as pipelines, pumps, disposal wells, ponds/storage treatment facilities, and other associated utilities infrastructure. The average cost for handling produced water starts from about $1.50/bbl, depending on the geographical location of the operation. Such costs may justify an assessment of an autonomous inflow control valve (AICV) to reduce unwanted water and gas to achieve OPEX savings. Horizontal wells are a proven option to maximize reservoir contact in certain situations. A challenge is often early water breakthrough in less than 6 months from starting production, and then progressively producing very-high water cuts, often 95%, for long periods of times thereafter. Inflow control device (ICD) technology has demonstrated potential in improving recovery in horizontal oil wells by delaying the gas and/or water breakthrough. However, ICDs cannot restrict water effluents once breakthrough occurs. A new generation of inflow control technology known as an AICV can balance the production flow and choke and shut the water-effluent zones once breakthrough occurs. Basis of Design The design is based on the Hagen-Poiseuille equation and Bernoulli’s principle. It uses the difference in fluid-flow behavior in the laminar- and the turbulent-flow restrictor to differentiate the pressure drop using the mobility ratio between oil, water, and gas. Light-viscosity fluids such as water and gas have high mobility and allow the AICV to detect the mobility difference, then choke and shut the main inflow area in the valve autonomously. Fig. 1 illustrates the construction of the valve in open positions, showing the direction of flow with arrows and the P1, P2, and P3 pressure locations. The inlet pressure is represented by P1: 2-5% of the main flow will move through the laminar-flow element (LFE) that will reduce the pressure to P2. Further pressure reduction occurs in the turbulent-flow element (TFE) to P3 as the tubing pressure. The differential pressure in LFE reacts to the piston’s effective area, resulting in a force balance around the piston to control the valve’s function (e.g., to open, choke, or close the main flow).