Existing practice in the drilling of horizontal and multilateral wells in Russia and specifically in Western Siberia often dictates the use of water base drill-in fluids. Horizontal section clean-up is typically accomplished by creating drawdown and back-flow of mud filter cake. Two main types of horizontal completion installations are commonly used – pre-drilled (slotted) and wire-warped liners, but more customers are moving into smart completion and starting to utilize more sophisticated screens.

With increased length of horizontal section and constantly depleting formation pressures filter cake lift-off pressure and ability to evenly remove filter cake from the reservoir face becomes critical to achieve target production rates and reduce time for well clean-up.

Also, in restricted completions, where filter cake might be held in place by completion assembly, water-wet filter cake establishes an impermeable barrier for crude oil and severely impairs well productivity.

External stimulation or removal of filter cake with breakers significantly complicates well completion, increases well construction time and cost and quite often does not deliver the expected results due to the uneven contact, early breakthrough and other factors.

To address the new challenges M-I SWACO has developed a water-based system that employs hydrophobic filter cake to reduce lift-off pressures where filter cake back-flow is possible (barefoot or slotted liner completions) or create oil-channels in the filter cake itself to allow formation hydrocarbons to pass through where filter cake is held in place by completion assembly (pre-fabricated wire-wrapped screens, open hole gravel packs and expandable screens).

Presentation will discuss the criteria used for development of the new reservoir drill-in fluid with organophilic filter cake, it’s advantages with regards to formation damage and well completion, actual results achieved with the new mud system on several Western Siberia oil fields.