Purpose -The purpose of this paper is to investigate the mechanical properties changing of geopolymer cement under different brine salinity. Design/methodology/approach -Geopolymer Cement of Class F Fly Ash and Class G Cement slurries were prepared according to API RP 10B. The optimum alkaline activator/cement and water/cement ratio of 0.44 was used for geopolymer and Class G cement samples, respectively. The alkaline activator was prepared by mixing the proportion of Sodium Hydroxide (NaOH) solutions of 8 M and Sodium Silicate (Na2SiO3) using ratio of 1:2.5 by weight. The slurries were cured for 24 hours at 130 o C and 3,000 psi in HPHT Curing Chamber followed by coring process. Both cement sample were immersed in brine water salinity up to 28 days with different brine salinity up to 30 per cent of NaCl. The mechanical properties were investigated using OYO Sonic Viewer-SX and Uniaxial Compressive Strength. The surfaces of the cement samples were extracted for Scanning Electron Microscope (SEM) and EDS tests to evaluate the morphology and chemical compositions of the cured samples. Findings -The paper shows that geopolymer samples experiences strength reduction in brine water but the reduction rate of geopolymer is about half of the Ordinary Portland cement based oil well cement. The finding was also verified by SEM and EDS result. Originality/value -This paper investigates the mechanical property changes of emerging geopolymer cement due to different water salinity. The results provide potential application of geopolymer cement for oil well cementing.
In this drilling campaign, out of 6 development wells, MPD/C were utilized in 4 wells. 1 well utilized both MPD for drilling and MPC for 7" casing installation (Well A) and the other 3 wells (Well B, C, D) were drilled conventionally and conducted MPC for 7" casing installation upon confirmed to have a narrow operating drilling window due to the depleted sands which verified by several MPD dynamic leak off tests (DLOT) during drilling resulted satisfied for conducting MPC for 7" 23ppf casing. In both conventional drilling or MPD wells, the job is guided by the drilling window which consist of the pore pressure/collapse pressure serves as the lower limits and fracture pressure serves as the upper bound of the window. The ability to control the well pressure profile with MPD system led to the Managed Pressure Cementing (MPC) as the alternative method implemented in this narrow pressure margin wells. MPC was planned in detailed by using the advanced MPD hydraulic modeling to model the surge effect of running in hole casing to setting depth and calculate the surface back pressure required to control the annular ECD/ESD during the different stages of cementing operation. Based on the surface back pressure target, the cementing parameters were designed and modelled accordingly to suit the cementing requirements. This paper presents the engineering design considerations, execution methods and results of four development wells with MPC operations conducted by closing the annular BOP to create the closed loop system to cement 7" 23ppf production casing strings successfully without losses events.
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