| Popis: |
Long known for its tolerance of solids-laden fluid and wellbore deviation, gas lift is an increasingly popular artificial lift method for horizontal unconventional wells. A variation of gas lift known as Single Point High Pressure Gas Lift (SPHPGL), noted for the absence of gas lift valves, is now practical because of the availability of high discharge pressure compression equipment. In SPE 187443 (Elmer 2017), the authors of this paper proffered that Annular SPHPGL could lift large liquid volumes. Further, this lift method was potentially a competitive alternative to failure prone Electric Submersible Pumps (ESPs) which are often used early in the life of horizontal wells to produce at high rates. The authors provided Nodal Systems Analysis to support this claim but lacked actual data from field testing. Finally, they appealed to industry to implement and perfect this "not new" but timely technology. When the referenced paper was presented at the October 2017 SPE ATCE, high pressure compressors were not available from industry for lease. This situation changed in early 2018, with rental equipment becoming available in the Permian Basin. Subsequently, a Permian Basin operator (SM Energy) agreed to perform a pilot test in Howard County, Texas to test the conclusions listed in the paper, primarily that Annular SPHPGL could compete rate-wise with ESPs. Plans for a pilot test were made. Additionally, the production facility was modified to handle the possibility of higher flowrates than normally observed with ESPs, as well as increased slugging. Injection down the tubing with returning flow up the tubing-casing annulus began in September 2018. Initial production rates were close to Nodal Systems Analysis predictions, and comparable with ESP flowrates. This proved that this technique could in fact compete rate-wise with ESPs. For operators using liquids-rich produced gas for gas lift, the importance of maintaining gas temperatures elevated throughout the compression process is documented. Also, the positive results of the production facility modifications to handle higher flowrates and possible slugging are presented. |
