HOT GAS INJECTION AS AN ARTIFICIAL LIFT SYSTEM THROUGH A CONCENTRIC TUBING COMPLETION IN A HEAVY OIL WELL
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This paper shows the results of the use of pre-heated gas (215 º F), which is used as a gas lift for wells producing heavy oil (ºAPI 12), based on experiences in a pilot test carried out in a well located in Pilon Field, MorichalDistrict. The principle of the lift system with concentric pipes is based on injecting hot gas through a 2-3/8-inch pipe, which has a special injection piece inserted at the end of the pipe and it is placed inside of a 4-½ inch production tubing, and the fluid is produced through the annular area created between the internal pipe diameter of 4½ inches and the outer diameter of 2-3/8 inch pipe. Theoil production rate in a gas lift well with 12 API gravity, as a result of the injection of hot gas, utilizing a completion of concentric tubing can be summarized in an increase of 57% in the production rate, from 520 bbl/day to 817 bbl/d, using the same gas injection rate (400 mscfd). With the concentric pipe system, a high efficiency heat transfer rate is achieved, due to the heat exchange iscarried out in countercurrent. The implementation of this system is of particular interest in heavy oil producing fields which produce by artificial gas lift. Furthermore, the hot gas injection for artificial gas lift is a competitive option when it is compared to diluent injection, with the purpose of increasing oil production in heavy oil wells, allowing this a higher lifting efficiency andtherefore reducing costs of oil and gas production.
The Morichal District is made up of heavy and extra heavy areas, with Pilon, Jobo, Morichal and Cerro Negro fieldsFields Morichal and Jobo have heavier crude (8.5 º - 11 º API) and Pilon has the lighter crude (11.5 º - 14 º API). The study was focused on the Pilon field. Pilon field there are a number of gas lift wells that are inactivedue to casing damage therefore the conventional gas injection can not produce, so it is necessary to use a completion with concentric tubing, where a pipe is inserted into a 2-3/8 inch production line 4 ½ inches, thereby isolating the area where the hole in the casing. In this way the gas will be injected through smaller diameter pipe and oil will be produced by the annular created between theinner diameter of the pipe 4 ½ inches and 2-3/8 inch pipe. These areas have specific characteristics that make oil extraction a complex process, due to high viscosity, which generates resistance to flow through the integrated production system (from the porous medium to the flow lines). In order to improve production and reduce oil viscosity, the implementation of hot gas injection system using anartificial lift completion of concentric tubes in a heavy oil well in the Pilon Field was conducted, which an increase in oil production over 50% was achieved.
large heat exchanger, thereby reducing viscosity of oil produced an increase well production.
The following table shows the basic information of the well where the evaluation was performed with hot gasinjection. Table 1. Basic information of the well Oil Gravity (°API) Reservoir pressure (psi) Reservoir temperatura, Tr (°F) Pay zone thickness (ft) Porosity (%) Permeability (darcy) Viscosity at Tr (cp) Water cut (BSW) 12 1250 130 117 26 4 800 45%
To calculate all equations for heat transfer involved in the system, it was designed a spreadsheet that allowed us to estimate the temperature...