First High-Temperature Applications of Anti-Gas Migration Slag Cement and Settable Oil-Mud Removal Spacers in Deep South Texas Gas Wells

Abstract

fax 01-214-952-9435. AbstractApplications of a new slag cement and spacer system have reduced the chance of gas channels forming in the cement column during cement hydration in deep, hot south Texas gas wells. These slag cements were formulated with water and conventional cement additives to prevent gas migration and to improve interfacial bonding to oil-wet surfaces. Oil-mud removal spacer fluids (OMRS) were also specially fOlmulated to remove oily residues and improve water-wetting of the oil-wet surfaces. These OMRS can also be designed to develop compressive strength when cementing operations have been completed.Set slag cement provides a tight gas seal with shear-bond healing capacity, as demonstrated by recently developed HTHP shear-bond strength tests. The previously reported phenomenon of healing or regeneration of slag-mix bonds has been reproduced with slag cement. The rapid development of strength at the top of the long cement column and the improved bonding to oil-wet surfaces were the two major improvements provided by the slag cement. OMRS can clean oil-wet surfaces, and then set once the job has been completed.Laboratory tests and field evaluations based on cement bond logs and pressure tests indicated improved bonding and isolation of the gas zones. Field applications of slag cements and OMRS fluids have led to greater primary and plug cementing successes in south Texas gas wells, and well production economics have improved accordingly.

Shale Cuttings Addition to Wellbore Cement and Their Effect on Unconfined Compressive Strength

“…Metakaolin is made from calcined kaolin clay and when added to cement, decreases the porosity and permeability, minimizes shrinkage, and minimizes chemical degradation [22]. Blast furnace slag formed during the manufacturing of iron has been shown to aid in preventing gas migration, setting time, and bonding [23,24]. Glass microspheres are a type of pozzalanic material that is used to lower the density of cement but have many drawbacks such as their cost, separation tendencies, and the tendency to be crushed under pressure [25][26][27].…”

Mechanical Properties and Microstructure of Slag Solidified Body

“…As such, the slag-based MTC technology of cementitious materials came into being [2]. The application of slag in the petroleum industries has a long history [3][4][5][6]. By adding an activator to activate the potential activity of the slag to form a solidified body with a certain strength.…”