Experimental study and modeling of water-based fluid imbibition process in Middle and Lower Indus Basin Formations of Pakistan

Abstract

Wellbore instability is one of the major problems that arise in drilling shale formations. Drilling in these formations may lead to breakouts and induce fractures. In Pakistan, drilling companies face quiet a number of formations that are shaly in nature and are candidates for wellbore instability issues. To counter these issues, it is required to have good understanding about the composition of the shale and its chemical reactivity with drilling fluids. Shale samples of three different formations have been obtained. These samples belong to two different regions of Indus Basin of Pakistan and were subjected to cation exchange capacity test and X-rays diffraction analysis to determine the reactivity and mineralogy, respectively. The samples were then tested for swelling properties using linear dynamic swell meter. The testing was done in two different water-based drilling fluids. The increase in height and swelling percentage for each sample was then recorded against each type of drilling fluid. A comparative analysis was done as to what type of drilling fluid systems out of the two used in the swelling test would best inhibit the swelling nature of shale for each formation in these regions of Pakistan. Finally, analytical and numerical modeling was performed on each shale sample. It was observed that the swelling parameter A (total swelling) increases significantly for Middle Indus Basin Shale Formation, and on the contrary, the filtration term (C) becomes independent of time after certain period of testing.

Metodología del diseño de un fluido de perforación base agua en la cuenca oriente ecuatoriana

“…Es importante para identificar el comportamiento de la formación a evaluar con una hidratación máxima y descontrolada (Khan et al, 2021), manifestándose como el hinchamiento y/o dispersión característica de…”

“…La capacidad de intercambio catiónico es una medida directa de la reactividad de sólidos de formación (muestra de cortes) expresada en meq/100g y que nos da una idea de que formación es más reactiva que otra (Khan et al, 2021). El método utilizado es una modificación del método del MBT.…”

“…Este método es efectivo para analizar la interacción roca-fluido bajo condiciones simuladas mientras el fluido está en movimiento (Khan et al, 2021).…”

“…El hinchamiento lineal (figura 3) mide con sensores de alta sensibilidad la altura de una pastilla cilíndrica la muestra y calcula su volumen, que lo compara con el estado inicial y entrega un porcentaje de hinchamiento cada segundo (Khan et al, 2021). De esta forma se obtiene una curva en función del tiempo donde el valor máximo es el hinchamiento lineal obtenido en un periodo de tiempo definido, en este caso se utiliza un tiempo de hinchamiento de 75 horas, tiempo aproximado que toma la perforación de la sección, viaje y corrida de revestidor, conocido como tiempo de exposición del hueco abierto.…”