The long term zonal isolation is an important factor to be considered while designing cement slurries for deep High Pressure, High Temperature (HPHT) gas well. Conventional heavy weight cement systems which have been used in the past have often had to sacrifice the set cement mechanical properties such as compressive strength, permeability, and porosity, to provide a slurry design which is stable, mixable and pumpable. Changes in downhole conditions in terms of temperature and pressure can induce sufficient stresses to destroy the integrity of the cement sheath which will cause long term gas migration and sustained annular pressure. Hence, the set cement mechanical properties have to be carefully designed in order to withstand the downhole stresses especially the ones generated during the well testing and fracturing treatments. This paper will discuss the selection and the Novel Flexible and Expanding cement system and details one well case history of nine wells which is part of the upstream agreement with Saudi.

An engineered fluid formulation was designed to provide a 114-pcf non-damaging drill-in fluid for the Unayzah A and B sandstone reservoirs. Employment of potassium formate high density brine and manganese tetra oxide weighting agent provided superior drilling properties that delivered reduced formation damage, improved thermal stability, and lower drilling costs.The use of acid-soluble manganese tetra oxide allowed engineers to increase the density of potassium formate drilling fluids and extend the density window above that offered by calcium carbonate. The reduced particle size (D50= 1 micron) and the spherical shape of the manganese tetra oxide reduced friction and drag. This improved control of equivalent circulating density (ECD) and plastic viscosity (PV) and significantly lowered rheological profiles. These optimal properties were maintained at temperatures exceeding 155°C.Laboratory testing confirmed high performance features such as: 1. Excellent hole cleaning characteristics 2. Thin filter cake with low lift-off pressures 3. Low differential sticking potential 4. Low treatment cost during drilling and re-use capability 5. Superior rheological performance compared to high solids content oil-based fluids 6. Improved drilling performance and hydraulic efficiency with the formate base system.The vertical well in the Unayzah A and B sandstone reservoirs was completed with zero hole problems. The potassium formate/manganese tetra oxide system provided superior performance and stability even with elevated bottomhole temperatures in the tight gas formation. This paper reviews the laboratory design and development as well as the field application of the high performance, brine-based drill-in fluid.

Long-term zonal isolation is an important factor to consider while designing cement slurries for deep high-pressure, high-temperature (HPHT) gas wells. Conventional heavyweight cement systems used in the past have often had to sacrifice set cement mechanical properties, such as compressive strength, permeability, and porosity, to provide a stable, mixable, and pumpable slurry design. Changes in downhole conditions in terms of temperature and pressure can induce sufficient stresses to destroy the integrity of the cement sheath, causing long-term gas migration and sustained annular pressure. Hence, the set cement mechanical properties have to be carefully designed in order to withstand the downhole stresses, especially the ones generated from well testing. A novel flexible and expanding cement system was chosen for the eighth well of project in Saudi Arabia.

Zonal isolation has extreme significance in the construction quality and life of a well. Achieving zonal isolation in deep highpressure, high-temperature (HPHT) gas wells is a challenging task, and these wells need more attention to achieve zonal isolation than conventional oil or gas wells. In addition to following primary industry best practices, the selection of a cement system appropriate for the environment of the well is very significant. Trapped gas and oil between production and intermediate casing (abnormal annulus wellhead pressure) has been globally recognized as one of the serious challenges facing drilling and production operations. The issue is becoming even more serious since wells are aging and the integrity of the casing portion below the well head is increasingly affected by the shallow-water corrosive environment. The potential safety and environmental hazards of the abnormal annulus pressure, have encouraged LUKSAR (Lukoil Saudi Arabia Energy Limited) to review the current drilling and cementing practices, with the goal of minimizing the impact of the problem, thus improving well life cycle and reducing the frequent work-over interventions. The general guidelines set to resolve the problem focused on eliminating potential leakage paths in the completion and casing strings and emphasized the quality of the primary cementing, especially for casings set on the aquifer zones and production casings. This paper discusses case histories and selection criteria for the different cement systems. It shows how high-performance lightweight sealant across weak zones, fiber-based sealant technology when lost circulation prevails, self healing sealant system where zonal isolation is extremely important, and flexible and expanding sealant for frac candidates are chosen for providing and maintaining well integrity in these extremely remote and challenging HPHT wells.

The aim of this study is to compare the properties of three self-compacted concrete (SCC) mixes, with normal concrete mix. For the SCC mixes, the cement was replaced partially with either limestone dust or clinker waste dust. Compressive strength, tensile splitting, and flexural strength tests were conducted at ages of 3, 7, 14, 28, and 56 days to trace the strength development. Modulus of elasticity tests were conducted at 28-days. The test results showed that mixes containing limestone dust have better fresh properties than the other SCC mix. The compressive strength test results showed that the mix containing clinker waste powder give higher compressive strength. and mix containing eight percent limestone give higher tensile splitting strength and flexural strength than the mix has ten percent of limestone give for all curing regimes. The results showed that the modulus of elasticity is relatively lower than that for normal concrete and the voids volume in normal concrete is greater than that of SCC.