Lost circulation during drilling operations is a costly problem that has plagued the oil and gas industry from its earliest beginnings. Drilling fluids are lost to the formation when the well is drilled overbalanced through high-permeability, fractured, or easily fractured formations. In many cases, total loss of circulation is experienced, and all drilling fluids are lost to the formation with zero returns to surface. This makes cementing casing strings and liners adequately into place difficult.
A range of commonly used conventional lost-circulation materials (LCMs) is available to combat lost circulation. These can be very effective in cases of low permeability or formations with small fractures where cement placement in the loss zone is relatively simple. However, in cases of severe or total lost circulation, the use of these conventional LCMs can often be ineffective. In such cases, attempts are made to stop the losses with the placement of dedicated lost-circulation treatments. These dedicated treatments include specialty cements, gel plugs, or even ordinary cement. However, severe cases of lost circulation continue to be a challenging problem.
This paper discusses field applications in a number of wells in the Burgos Basin of Mexico. A temperature-activated, rigid-setting fluid composition was developed specifically to address the most severe cases of lost circulation. In each of the wells presented, total lost circulation was encountered and treated successfully, allowing drilling operations to resume and the wells to be drilled to the designed depth. This paper details the specific chemical and mechanical characteristics and field performance of the rigid-setting fluid (RSF). It concludes that the combination of unique fluid properties and best practices in fluid placement procedures resulted in a very positive and successful development in the treatment of severe cases of lost circulation in sandstone formations.