FORMATION DAMAGE
In the drilling, formation damage can be caused by a factor of drilling fluid and drilling mechanical problems. Formation damage that caused by drilling fluid factors first occurs when invasion of drilling fluid or filtrate or solid into the formation during drilling takes place.
In conventional drilling fluid invasion factor will be difficult to avoid, especially in the use of heavy mud.
Invasion of the fluid / filtrate / solid can occur either in production formation or reactive shale zone. Both zones are worth to be maintained in order to avoid shrinkage or swelling on the clay colloid of rock that will cause blockage and or solid that will fit into the pores of the rock formations.
In reactive shale zone then this invasion will be able to cause stuct pipe as well as caving or even well packed pack off.