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

Indonesia : Well Teresia AC-6

Summary: The ESP in Teresia AC-6 regularly trips from shale/scale buildup and normally requires pump replacement or extended spotting periods with complex solvents and chelating chemicals. Cleaning with the Koplus LO + Ferrout 301 regime needed only 21.5 hours to put the well back on production with no overload on the ESP. The formation was also unexpectedly stimulated when it more than doubled the oil production, resulting in a payback time of 31 hours.

The Operator has chronic problems with the build up of short term shale/scale deposits in 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, pump cleaning 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 Teresia AC-6 ESP had been in service for 211 days producing between 150 to 175 BOPD when it went into over load and tripped out. Attempts to re-start the ESP were unsuccessful and no mechanical or electrical faults were noted. This well was noted for its high scaling potential and the tightness of the formation. It was suspected from previous pumps removed from this well that scale had built up between the diffuser and the impeller.

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, allowing it to soak for 8 hours. After 8 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. After seven hours of start up the well began producing 175 BOPD with no over load on the ESP, cleaning up to 396 BOPD after 36 hours of continuous production and then levelling to 300 BOPD. The payback time was 31 hours but more importantly, the pump did not require replacement.

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

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