First Implementation of Ultra High Compressive Strength 12.5 ppg Cement Slurry in Production String in Kuwait Oilfields

Abstract

Quality Cementation across production sections consisting of depleted/weaker formations is the main challenge in Kuwait. Usage of conventional cement slurry over 15.8 ppg will lead to losses and poor zonal isolation. Newly designed 12.5 ppg enhanced compressive strength cement slurry was proposed to achieve desired zonal isolation and well integrity while avoiding losses and unnecessary remedial jobs. Strategy was formulated to minimize exposure of weaker formations for higher ECDs during cementation. Conventional 15.8PPG tail slurry was replaced with 12.5PPG Ultra high compressive strength (4000psi) cement slurry. New slurry design helped to carry out cementation job without any losses while achieving rapid compressive strength and excellent cement bond across production casing. The technology is based on three radical changes in the conventional way of designing cement Slurry of Substitution of part of the cement volume with inert agents of low specific weight, High packing density using solids of different sizes, and Reduction of water volume required. The job was performed safely and successfully, no losses was observed during and after the cementing job while getting pure cement returns at surface during both stages of cement job. CBL/VDL was performed 24 hrs after the cement job; and the results were excellent. The main advantages of this technology are: Ø High resistance to compression: Once the slurry has set, it is capable of developing compressive strength values ​​similar to heavier conventional slurry. Ø Low reactivity: Most of the elements used are chemically inert, this facilitates the design of the slurry by reducing adverse chemical reactions. Ø Low Shrinkage of Cement: Due to the reduction of the volume of the Portland cement in the slurry, the shrinkage of the set cement is reduced, which allows a better adherence of this to the formation and to the Casing. Ø Mix-ability: Does not require special equipment for its preparation, as if foamed cements require it. Three case histories will be presented with all data and evidence, showing design phase, planning phase, execution phase and results obtained with all logs were showing the excellent results were achieved. This technology has several applications in the industry, which can be executed satisfactorily.