Can drilling fluid / mud protect a shale formation?

The drilling fluids / mud cannot permanently protect the formation against this deterioration. However it can mitigate the effect by providing a restraining differential pressure to hold the failed pieces in place. To maintain this protection until casing point the fluid must resist pressure equalization into the shale for that length of time.

Can PAC be used in shale drilling?

Application is limited to the shales that produce actual cuttings during drilling (medium to hard). The soft shales mechanically disintegrate too easily, and every small particle of shale will take up polymer. This consumes expensive material for no benefit in keeping the particles together. PAC is a modified CMC.

What happens when polyglycol is soluble in mud?

These molecules are normally soluble in a drilling fluid / mud at surface conditions. When the temperature passes a critical point, the polyglycols change to an insoluble phase; this transition is called the cloud point. The resultant microgels are large enough to block the shale pore throats and stop pressure transmission.

How are salt polymer drilling fluids selected?

The drilling fluid properties are investigated to determine the performance levels required. Additives are compared against the models. The economics of the various products are then evaluated to select the optimum fluid for the well. The salt polymer drilling fluids systems follow the same basic makeup.

Is Koh a stabiliser for reactive clays?

KOH has been promoted as a stabiliser for reactive clays. However, the OH radical is the prime clay dispersive element; therefore this reaction is dubious. Complexing of the phosphate anion with the exchangeable cations can preclude cation exchange and water imbibition. The most commonly employed forms are PO 4– or P 2 O 7–.

How do you manage inhibitive drilling fluid?

A key requirement for effective management of the inhibitive drilling fluid is single function additives. Individual properties can then be adjusted without interference to the other properties. This is essentially for maintaining overall efficiency.