Abstract

This paper uses case studies to showcase the techno-economic impact of insert anchor and portable foundation on the development of marginal fields. Case studies are also included for unconventional surface pumping unit – Linear rod pump and hydraulic rod pump in the development of multiple wells from a single wellpad.

Cairn India Ltd. is developing the southern part of its RJ-ON-90/1 block consisting of multiple geographically dispersed marginal fields, with small oil pool and varying crude properties. These fields consist of wells from exploration and appraisal era (some as old as 20xx[AD1]) completed for a natural lift with no provision for installing artificial lift system. Later, it was recommended to install Sucker Rod Pump (SRP) as the most suitable Artificial Lift (AL) system. Conventionally sucker rod down-hole pump is installed by running a barrel assembly on the bottom of tubing and plunger assembly at bottom of rod string. However, in an insertable sucker rod pump (ISRP), the entire pump assembly is run-in at the bottom of rod string and is landed on pump seating nipple (PSN) which was originally installed in the tubing string. Hence, installing SRP would require an expensive work-over operation.

As the oil prices dropped, the economics of work overs became less justified. Options reviewed to improve the field economics included the use of Insertable pump anchor for installation of through tubing down-hole pump in existing well. This method allows setting the down-hole pump in tubing string without any requirement of pump seating nipple. The anchor provides the flexibility of pulling out and re-installing pump with the new or redressed system in case of pump malfunction or pump size modification etc. Extended application of insert anchor includes flow-back of hydraulic-fractured wells and extended well testing in exploration fields. It provides the flexibility of changing pump size based on reservoir response at the later stage. The multiple set-reset mechanism of insert anchor enables identifying tubing leaks and setting the pump above it.

A portable concrete foundation against the conventional concrete base used for surface unit erection provides the flexibility of transporting the foundation between different locations. The foundation can be de-mobilized while placing the work-over rig, which otherwise requires disassembling fixed foundation. The same foundation can be used at multiple well sites saving on the cost of construction and reduced lost production time.

On multi-well welllpad system, erection of conventional surface pumping unit on adjacent wells came as big challenge due to space constraint between the wells. Moreover, in the case of any well intervention like work-over, rod change etc. the nearby units requires to be disassembled adding to oil loss. Considering these problems operator decided to look into unconventional surface pumping unit e.g linear rod pump and hydraulic rod pump for the well pad systems.

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