CASE HISTORY - ESP Cleaning and Perforation Stimulation using Koplus LO + Ferrout 301

Indonesia : Well Zelda AC-1

Summary: The ESP in Zelda AC-1 went into overload losing production of between 279 to 387 bopd. The well as treated with Koplus LO + Ferrout 301 with the chemicals left in the well bore after verifying the restoration of the ESP function. The tubing was pulled and replaced, leaving the Koplus LO + Ferrout 301 spotted across the perforations during this period. On re-running the tubing, with the original ESP, production was found to have increased to 1046 BOPD – a 300% increase.

The Operator has chronic problems with the build up of short term shale/scale deposits in their down hole electrical submersible pumps (ESP) in a number of fields. The pumps typically can reach overload in less than 30 days or can last 300 days (or more) of production life if chemical cleaning is successful. More often than not, it has been necessary to replace the pumps completely.

Historically, cleaning of the pumps involved the pumping of complex solvent and chelating (EDTA) based chemicals across the wells and soaking for extended periods of time. One other concern is the corrosive nature of these chemicals. Terra Expro examined the debris and the actual pumps, concluding the length of time a pump had been exposed down hole determined the type of treatment required to clean the pumps and remove the blockage debris.

In this approach, Terra Expro programmed two distinct treatment regimes. The first was for pumps designated as “younger” or having been in place less than 180 days with the second type designated as “older” which had been in service continuously or otherwise for much longer than 180 days.

The Zelda AC-1 well had been in service producing 279 BOPD, when it went into over load and tripped out. Its peak production had been in excess of 1000 BOPD in 1999, but has since declined steadily. The ESP on this well failed and attempts to restart the ESP were unsuccessful and no mechanical or electrical faults were noted.

A treatment of 150 liters of Koplus LO was programmed for spotting across the pump in a single 90-minute soak as a pre-cleaning solution. The second stage entailed placing 155 gallons of Ferrout 301, a high performance sulphide and carbonate scale dissolver, across the pump and allowing it to soak for eight hours. After eight hours, the Ferrout 301 was displaced to 155 gallons of fresh Ferrout 301 and the well shut in for 12 hours. Note: Unlike the chelating chemicals, Koplus LO + Ferrout 301 are non-corrosive.

After a total treatment period 21.5 hours, the pump was engaged, and operating at full potential without tripping. The pump was disengaged and the Ferrout 301 and Koplus LO pumped back down through the pump and allowed to soak across the perforations. During this soak period, the ESP was pulled and the tubing replaced. After the intervention the well began producing 1046 BOPD with no over load on the ESP, maintaining this production without decrease for over a month before this report was prepared and is still producing at that rate.

BEFORE : Typical ESP impeller and diffuser – pulled due to scaling.

AFTER : The same components as above after cleaning with Koplus LO & Ferrout 301.