Mechanical, Rheological and Microstructural Properties of Saudi Type G Cement Slurry with Silica Flour Used in Saudi Oil Field under HTHP Conditions

Abstract

With the continued growth of petroleum demand, the oil and gas companies are searching in new or unexplored areas. The search is getting extreme in terms of depth, temperature and pressure. In deeper wells, high temperature and pressure and post cementing operations put extreme stresses on the cement sheath and affect the integrity of the cement. In such conditions, the design of cement slurry is very critical and it must possess properties which ensure the durability and long term integrity of cement sheath. The purpose of this study is to evaluate the physical properties of Saudi cement class G with silica flour and admixed with different additives such as fluid loss agent, retarder, expanding agent and friction reducing agent under high temperature and pressure conditions. In this paper, we present the results of experimental investigations conducted on class G cement slurry without additives, as a basis, and cement slurry with additives and silica flour. Free water separation, rheological properties, compressive strength, density, scanning electron microscope (SEM), X-Ray diffraction (XRD), porosity and permeability tests were conducted with and without additives at both room and HTHP conditions.

Geopolymer cement slurries with enhanced mechanical and physical properties for oilwell cementing

“…In addition, when subjected to temperature in excess of 230°F (110°C), C-S-H phase undergoes transformation that alters mechanical strength, gives high permeability and strength retrogression [2]. Comparing to the data obtained in regards to geopolymer cement, it is contradict as the strength develops with the curing time.…”

“…Early strength development is important in ensuring structural support to casing, hydraulic and mechanical isolation. It also can be set in the presence of sulphate water, be a pump able slurry and produces no lumps, remain fluid until close to setting time, do not produce excessive heat during setting of cement and has low permeability [2].…”

“…Inadequate presence of silica, will convert C-S-H phase into lime rich α-dicalcium silicate hydrate. α-dicalcium silicate hydrate create high permeability and strength retrogression in cement mix [2,4]. Strength retrogression can be defined as reduction in cement strength to the point of failure due to exposure of high temperature [5] while permeability is the ability of fluid to flow at different temperature between cement particles [2].…”

“…Low permeability of cement will result in good long term performance of cement [2] while high permeability may lead gas percolation, result in pressure accumulation behind low portion of the well. It also may cause blow out, weaker zonal isolation and production losses [6].…”

“…This is due to the high amount of silica fume incorporated in it, in which high degree of pozzolanic reaction induces higher compressive strength development [13]. The fineness of silica fume forms dense matrixes that enhance the bonding and thus gave strength to cement [2].…”