Flexible, Self-Healing Cement Eliminates Sustained Casing Pressure in Denver-Julesburg Basin Unconventional Wells

Abstract

The oil and gas industry has operated in Denver Julesburg (DJ) basin for many decades. Currently in the basin, increasing population density and wellbore complexity have resulted in a heightened visibility of long-term well integrity. Failure can lead to future liabilities, loss of public trust, and a revoked right to operate. Operators must demonstrate commitment to well integrity to continue operating in the basin, yet many still report sustained casing pressure (SCP) on a significant portion of wells. Because SCP corresponds to the open communication of fluids to surface, it is a direct metric of well integrity failure. Regulations require operators to report and remediate instances of SCP on all wells. On average, clients experience one well with SCP for every five drilled. As a primary well barrier element, the cement sheath is vital to well integrity improvement. Enhanced placement techniques of conventional cements failed to prevent SCP, confirming that failure is derived from post-placement dynamic conditions. The solution must account for pressure and temperature stresses, preventing and mitigating mechanical failures throughout the well life cycle. A flexible and self-healing cement design provides a twofold response that is ideal for wells in areas, such as the DJ basin, with SCP risk. Mechanical properties are optimized based on the results of a mathematical stress model. Although Portland-based cement systems can be optimized to sustain higher levels of dynamic stresses, it is impossible to avoid a mechanical failure entirely. Therefore, a self-healing function is a critical secondary feature. The self-healing mechanism is designed to activate upon contact with an invading hydrocarbon and can be formulated for any type of hydrocarbon, from high gravity oil to dry gas. Flexible and self-healing cement has been successfully designed and implemented on approximately 250 wells in the DJ basin with a reduction to 2% instances of SCP. Elimination of SCP provides confidence in long-term well integrity, which is essential to continued operation in the basin.

Advanced Solutions for Oil-Well Cementing in High-Pressure High-Temperature Oil Wells Using Nano-Gilsonite

“…21 Additionally, SHC functions exactly like regular cement without hydrocarbon exposure. 22 Once the cement operation is finished, an SHC-containing gilsonite is durable in the long run to reduce microannular flow. Gilsonite is a good choice for both a cement additive and a component of an SHC because of its good compressive strength and capacity to withstand high temperatures.…”

“…17 When self-healing cement additives are exposed to unwanted hydrocarbons, they automatically close annular channels, preventing remedial cementing, plugging, and wellbore abandonment. 22 Gilsonite is a nonhazardous, naturally occurring hydrocarbon resin made up of a considerable number of pyrrole and aromatic chemicals. Figure 1 illustrates the structure of natural gilsonite.…”

“…Gilsonite, an additive to wellbore cement, is reported to provide self-healing qualities that could be useful in reducing integral problems . Additionally, SHC functions exactly like regular cement without hydrocarbon exposure . Once the cement operation is finished, an SHC-containing gilsonite is durable in the long run to reduce microannular flow.…”

Application of Geomimicry to Engineering Problems:gilsonite as a Solution to Leaky Wellbores

“…Mitigation to gas intrusion could be achieved using self-healing cement additives. Self-healing cement additives have the potential to avoid remedial cementing or plug and abandonment of the wellbore by automatically sealing annular pathways after being exposed to unwanted hydrocarbons (Langley et al 2018). The additives remain dormant in the cement sheath until hydrocarbon migration occurs.…”

“…Reduced costs of cement remediation and lost circulation loss in cement integrity while also the potential to improve productive life of the make using SHC an economical and time efficient decision if applicable. (Langley et al 2018). It is important to note that the concept of SHC does not preclude the importance of good cement practice, but rather improves the ability to mitigate micro annular fluid migration.…”