DRILLING OF OIL AND GAS WELLS IN UNSTABLE CLAY FORMATIONS

Abstract

During drilling operations in oil and gas fields, a long-term, stable, and well-isolated channel must be created to connect the productive formation with the surface. Drilling and cementing fluids play a crucial role during well construction. Not only the efficiency of drilling operations, but also the service life of the well depends on the ability of these fluids to perform their functions under various geological and technical conditions.The commonly used terms drilling fluid, circulating fluid, or cement slurry do not fully reflect the physicochemical nature of these systems; their usage is largely based on industry tradition. In terms of composition, these systems should be classified as complex polymineral dispersions stabilized by surfactants (surface-active agents) [1].

Despite the large number of studies proposing formulations for drilling fluids based on modern technologies, there remain significant challenges when drilling deep wells. These challenges are associated with the need to adapt existing technologies to the lithological, reservoir, and thermobaric characteristics specific to the drilling region. Deep formations characterized by abnormal (low or high) formation pressures exhibit several distinct features.

In the conditions typical of Kazakhstan, unstable clay sediments are highly hydrophilic. As a result, their interaction with the aqueous phase of drilling fluids and the effect of hydrostatic pressure lead to swelling caused by hydrodynamic pressure (up to 20%) and physicochemical processes occurring in the annular space (up to 64%).