Arcasolve™ Mud Damage Removal System

Drilling a wellbore results in formation damage. Deposition of a filter cake during drilling effectively seals off the formation. Filter cakes typically contain solids (frequently carbonate) arising from the bridging/weighting material present in the drilling mud or drill-in fluid, polymer from the drilling mud or drill-in fluid (where water based) and formation fines material produced during the drilling process. Spurt losses during filter cake formation and leak-off results in bridging material, fines and polymers entering the formation causing additional damage behind the filter cake.
This damage (skin) can severely limit the production (or injection) rate of the well making effective clean-up very important.

The increasing use of long horizontal wells which have very low draw-down makes effective damage removal ever more challenging, particularly in low permeability formations, partially depleted low pressure reservoirs and injector wells.

Significant financial benefits may be obtained from removing damage (skin) present as a result of drilling. Effective removal of skin helps maximises the production (or injection) rate and NPV of the well.

Ideally, filter cake damage will be completely solubilized. Conventional approaches to removing damage include the use of mineral acids, enzyme polymer breakers, polymer breaking oxidants or combinations often using separate treatment stages.

However, oxidizers or enzyme polymer breakers alone cannot remove all of the damage as they attack the polymers but do not dissolve carbonate or other acid soluble materials, so may leave significant damage behind. Enzymes may be placed using the drillstring but generally operate under suboptimal conditions of pH; most polymer degrading enzymes prefer slightly acidic conditions.

There are problems in placing mineral acid, especially in very long horizontal wells where placement through the drillstring may not be possible. There use of coiled tubing (CT) is generally costly and may have operational limitations in long and/or deep wells. Even when spotted through drill pipe or CT, conventional reactive acids tend to prematurely penetrate mud cake on contact, leaking off to the formation, instead of filling the horizontal wellbore to uniformly acidize and remove damage across the entire wellbore face. This can result in patchy cover in long horizontal/directional wellbores.

Conventional acids such as hydrochloric acid (HCl) have a number of key, fundamental limitations:

Their fast reaction rate with carbonate or other acid soluble material gives poor zonal coverage.
There are significant Health and Safety hazards involved in handling acids, particularly when pumping them at high rates and pressures (frequently used to try to improve zonal coverage).
Conventional acids are highly corrosive, generally requiring the use of expensive corrosion inhibitors which are often toxic and/or have poor environmental acceptability.

Cleansorb has developed its patented Arcasolve™ acidizing process for the highly efficient treatment of drilling fluid damage which by overcomes the key limitations of systems based on conventional acids or other breakers:

Arcasolve™ acidizing fluid is initially non-reactive and non-corrosive and can be placed in the wellbore via the drillstring during completion operations.
Following placement, organic acid is produced homogeneously throughout the fluid giving excellent zonal coverage; the entire wellbore is effectively acidized. Arcasolve™ acidizing alone may achieve highly effective removal of filter cake.
Arcasolve™ treatment fluid is low hazard to handle and use and has very low environmental impact.
Where mud damage includes polymers, polymer breakers can be incorporated into the Arcasolve™ formulation to give simultaneous acidising and polymer breaking in a single stage treatment. The acidizing products actually help buffer the fluid at an ideal pH for optimum performance of Cleansorb’s polymer degrading enzymes.

Arcasolve™ is highly effective for damage removal. It delivers acid evenly along the whole of even a very long horizontal wellbore, producing uniform damage removal and stimulation which is difficult if not impossible to obtain with other approaches.

Visualisation of Drilling Damage Removal using Arcasolve™ Compared to Other Methods

Damage Removal and Optimising Horizontal Well Performance

More about Arcasolve™ for drilling fluid damage removal