Divergence of Dynamometer Card Analysis from Actual Field Results at Light and Heavy Oil Fields of Mehsana

Abstract

Abstract The performance of rod pumped wells are analyzed based on routine monitoring methods of echo meter and dynamometer analysis. There are 1080 sucker rod pumps installed in various fields of Mehsana. Rod pumps fail due to rod-tubing wear and aggressive fluid-reservoir conditions. Diagnostic studies are carried out promptly to predict the cause of rod pump failure. Circulation and crane troubleshooting jobs are taken post-diagnostic jobs to confirm the failure mechanism. This paper will discuss prominent mechanisms of rod pump failure, the use of dynamometer cards to track failure, and troubleshooting jobs to prevent failure. In heavy oil fields, when the pump ceases to flow, the acquired dynamometer card showed a standing valve or traveling valve or both choked up. During troubleshooting by crane, polished rod load depicted sucker rod unscrewing or parting. The reasons for the divergence of dynamometer cards from troubleshooting jobs are the variation of fluid load due to fluid characteristics. The accessed dynamometer card indicates gas interference or gas lock despite low casing head pressure in light oil fields. During circulation job execution, the initial pumping pressure of the surface pump is quite high, which indicated obstruction across the subsurface pump. The obstruction causes no freefall of polished rod, requiring servicing by workover rig. During the pullout of the subsurface pump by workover rig, observations included downhole screen choked, gravel pack failure, wax deposition on sucker rods subsurface pump, and tailpipes choked with fine sand. Solids incursion in light oil fields and rod unscrew in heavy oil fields are difficult to differentiate on basis of dynamometer cards. This paper will be fruitful to operators in identifying the cases, where the dynamometer card interpretation and analysis deviate from field practices.