rheological study of a water based oil well drilling fluid

2023-06-13

Oil well drilling operations require a fluid to be used as a lubricant for the drill bit, remove any particles of matter dug from the well, and maintain pressure within. This liquid – known as a water-based mud – is created from water, clay, and specific additives to achieve the desired rheologic properties for maximum performance.

Rheology examines the behaviour of materials when they are subjected to certain forces – and it has some particularly interesting applications when it comes to the world of drilling. The flow and ability to deform of a fluid play an integral part in drilling, as it affects the lubrication of the drill bit, helps lift cuttings from the borehole, and assists in keeping a steady pressure beneath the surface.

Upon reaching a certain level of pressure, fluids undergo a transformation from being liquid to solid. This pivotal event, the yield point, plays a major role in defining the consistency of a fluid and subsequently impacts its overall fluidity. Simply put, a fluid exhibiting a high yield point is much thicker and will flow with greater difficulty than one with a low yield point.

With regards to its resistance to flow, plastic viscosity provides information necessary for gauging a fluid’s ability to act as a lubricant during a drilling operation. Compared to one with a lower viscosity level, a fluid exhibiting a higher plastic viscosity composition will be stickier and naturally flow at a much slower pace.

When it comes to fluidity, resistance to shape alterations serves as an effective measure. That is because the gel strength of said fluid directly determines its effectiveness when it comes to removing cuttings. Generally speaking, a fluid with a high gel strength will be thicker, thus flowing rather reluctantly, when compared to one with a low gel strength.

By employing a rheometer, which lets one evaluate the flow of a fluid, the rheology of a drilling fluid can be uncovered. This novel tool ascertains the fluid’s yield point, plastic viscosity, and gel strength precisely and accurately.

The properties of a drilling fluid can be altered with different clay types. This can determine if the fluid has sufficient viscosity or gel strength to be effective. Furthermore, this composition will also adjust the rate of flow and lubrication of the drill bit, enhancing its ability to produce and remove cuttings.

When producing mud for drilling, the type of clay usually selected can have a significant effect on the viscosity of the output. This is important since the fluid’s density plays a major role in its capability to withstand well pressure. The greater the density, the thicker and slower-moving the fluid will be. In contrast, more liquid-like fluids are characterized by lower densities.

The construction of a drilling fluid primarily relies on its rheological properties, which are informed by the chemical ingredients used to create the mud. Such components considerably alter the fluid’s flowability, capacity to lubricate the drill bit, and potential to remove cuttings from the borehole.

The rheometer is tasked with testing the rheological elements of a drilling liquid, gauging its yield point, plastic viscosity, and gel strength. This procedure is crucial as it impacts the ability of the liquid to handle its role in drilling: allowing the drill bit to move easily, getting rid of the accumulations and sustaining pressure throughout the well.