1. ROBERT GORDON UNIVERSITY 2015
OSVALDO NELSON ANTÓNIO TCHISSOLA 1
Hole Cleaning Optimisation model
Osvaldo Tchissola-1009243
MSc Drilling and Well Engineering 2015
Abstract
Hole cleaning consists of efficiently removing the cuttings from the hole to
the surface by pumping drilling fluid through the drilling string and returning
it through the annulus. For vertical wells this process is well understood and
easily managed. But as the reach of directional wells increases, the process
becomes challenging, making hole cleaning the major concern that must be
properly addressed from the design stage through operations and well review.
Optimum hole cleaning depends on several factors, such as inclination angle,
drill-string rotation, mud rheology, cuttings size and flow rate, just to name
a few. A good understanding of how each of the factors will impact on
transport of the cuttings is required to obtain a good cleaning operation. If
the cuttings are not transported to the surface efficiently, several hole
problems, such as excessive torque and drag on a stuck pipe, may arise that
will impact negatively on the whole operation.
This project presents a simple integrated model for hole cleaning optimisation
that can be used from the design stage of the well and during drilling
operations to anticipate and avoid hole problems due to poor hole cleaning at
an early stage. It can be used for low angle and high angles wells.
The model estimates the optimum parameters to ensure that the cuttings are
continuously moving with the drilling fluid. The real-time data can be fed or
input manually into the model for real-time monitoring. The base of the
analysis is material balance of the cuttings, annular pressure loss and friction
in the annulus.
Another concept presented by the model is the estimation of the time required
to circulate after drilling has reached the total depth. The concept helps to
estimate the circulating time required at the TD to have all the cuttings at the
surface. The results of the model were found to be acceptable, but need
further work with field application to prove its utility.