The use of Self Healing Cement to Ensure long Term Zonal Isolation for HPHT wells subject to Hydraulic Fracturing Operations in Pakistan

Ekpe³

et al. 2010

All Days

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.

Cementing in HPHT Gas Environment Using a Novel Flexible And Expandable Cement Technology To Withstand Pressure And Temperature Cycles

Al-Thuwaini

Ekpe³

et al. 2010

All Days

Deep Tight Gas Zonal Isolation Solution with Novel Flexible and Expandable Cement Technology

Al-Thuwaini

SPE EUROPEC/EAGE Annual Conference and Exhibition

Belousov³

et al. 2010

Self Cite

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.

Fit-for-Purpose Sealant Selection for Zonal Isolation in HPHT Deep Tight Gas Wells

Al-Thuwaini¹,

Ekpe³

et al. 2010

All Days

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.