Polyglycol provides superior shale inhibition property and wellbore stabilization due to chemical adsorption and unique chemistry of poly glycols.
Chemical adsorption though applicable both below and above cloud point, is greater when glycol has clouded out and is in colloidal form, thus resulted in glycol-coated clays that are somewhat water repellant.
As the temperature cools, the glycol becomes more water-soluble and a grater portion of inhibitor is retained in the drilling fluid.
The inhibition mechanism can be readily combined with more traditional cation exchange and encapsulating mechanisms to provide the excellent inhibition characteristics of the polyglycol drilling fluid system.
Shale inhibition is improved when the polyglycol is insoluble or ‘clouded out’ state when it provides a barrier against water migration into the shale while it plugs shale pores to prevent the equalization of hydrostatic pressure away from the well bore.
‘Cloud point’ is the temperature where poyglycol additives change from being soluble (at lower temperatures) to being insoluble (at higher temperatures). The cloud point temperature can be reduced by increasing the salinity (or other electrolytes) or by increasing the concentration of polyglycol.
The improved shale inhibition of polyglycol leads to lower dilution volume, fewer hole washouts and reduced instances of stuck pipe, which translate into less waste volumes requiring disposal and more pollution prevention and source reduction opportunities. Using the polyglycol system, at temperature above its cloud point, through a producing reservoir will significantly reduce invasion into the reservoir, and no glycol will be present in the filtrate. This gives rise to extremely low skin factors and, coupled with an easily removable filter cake, makes the polyglycol system applicable for non-cemented completions.
By engineering the system so the polyglycol cloud point matches the downhole temperature, maximum benefit can be obtained. Above this temperature, the glycol forms a type of micro-emulsion which is often referred to as a “Thermally Activated Mud Emulsion” (TAME).This TAME effect contributes to stabilizing the wellbore in three distinct ways:
Micro-emulsion and precipitate pore plugging
Filter cake improvement.
CRISTOL-LC LUBE is a versatile-cloud-point glycol designed specifically for fresh to medium salinity poly glycol system. The primary function of this glycol is shale inhibition as it inhibits swelling shales and clays by adsorbing onto clay surfaces. It also helps to improve well bore stability, lubricity and high-temperature filtration control, in addition to reducing dilution rates and bit balling. While such polyglycols are most effective when used in conjunction with an inhibitive salt in non-dispersed polymer systems, they can be used as additives in most water-base systems.
Typical Physical Properties
1 Form : Liquid
Specific Gravity @ 20°C ± 2°C : 1.015 – 1.040
Cloud point of 3% in 10% Kcl Soln : above 90°F (32°C)
Cristol-LC LUBE has applications in polyglycol systems in fresh to medium salinity fluid systems and can be used in wells with low formation temperatures. These polyglycols systems are non dispersed polymer systems utilizing an electrolyte to activate the cloud point glycol. When clouded out this glycol strongly binds to the surface of troublesome shales forming a water repellent barrier thus minimizing the effects of troublesome water sensitive shales on drilling process and mud properties.
CRISTOL-LC LUBE also help provide significant reduction in mud dilution rates, reduced friction coefficients, and enhanced rate of penetration.
• 0.5-5% by volume. Concentration depends on salt type, concentration as well as the
down hole temperature range.
Improved well-bore stability and shale inhibition
Improved lubricity and higher penetration
Improved high-temperature filtration control
Reduced dilution rates, friction coefficients and mud consumption
Reduced Bitballing Potential
Good compatibility with all water-base systems and other glycols
Compatible with most salts
Toxicity and Handling
Handle as an industrial chemical, wearing personal protective equipment and observing the
precautions as described in the Material Safety Data Sheet (MSDS).
Packing and Storage
Store in dry, well-ventilated area. Keep away from heat, direct sunlight, sparks and flames. Follow safe ware-housing practices regarding palletizing, banding, shrink-wrapping or stacking.