BAKER HUGHES - Drilling Fluids Reference Manual

TABLE OF CONTENTS
HYDRAULIC MODELING SOFTWARE
INTRODUCTION
In deepwater drilling operations it is extremely important to have control over the Equivalent Static
Density (ESD) and the Equivalent Circulating Density (ECD) at all times. This is due, in part, to the
young formations associated with deepwater drilling and the types of fluid normally employed to drill
these wells. Overwhelmingly, invert emulsions are used in deepwater, with the external phase being
decided by environmental regulations or operator policy. Invert emulsions are very inhibitive and
offer excellent rates-of-penetration. There are a host of other advantages to invert emulsions covered
early in this section (see section titled: AQUEOUS VS NON-AQUEOUS DRILLING FLUIDS).
Non-aqueous fluids are compressible and expandable under the wide range of temperatures and
pressures they are subjected to in a deepwater environment. Therefore, it is imperative that
corrections are made to the fluid properties to compensate for the temperature and pressure effects on
the whole mud density and rheological characteristics under downhole conditions.
Baker Hughes Drilling Fluids has two state-of-the-art modeling programs to assist in analytical
solutions for our customers; Presmod, which is primarily used to determine dynamic temperature
profiles and ADVANTAGE SM , which is Baker Hughes Drilling Fluids proprietary hole cleaning and
hydraulics model.
TEMPERATURE MODELING
Presmod
Presmod is a dynamic hydraulics/temperature simulator. Presmod is capable of predicting ECD,
ESD and temperature profiles of the annulus and drill string as a function of time. However, Presmod
should not be used to predict ECD since the program assumes 100% hole cleaning, regardless of flow
rate or other hole cleaning variables.
For deepwater applications, Presmod is primarily used to predict dynamic temperature profiles when
there is potential for the occurrence of gas hydrates. In practice, Presmod is used for the following
scenario:
An upper section of a deepwater well is drilled with an aqueous fluid which is limited by the amount
of salt that can be added due to density restrictions. Also, the volume of liquid additives (glycols,
alcohols, etc.) necessary to ensure against hydrate formation is cost prohibitive and would be
detrimental to the performance of the fluid system. The section is drilled to total depth (TD) and the
fluid reaches a circulating temperature profile. The two issues to address are:
1. What will be the final annular circulating temperature? And in particular, what is the
temperature at the mud line when drilling ceases, prior to tripping out to run pipe?
2. Under non-circulating conditions, how long will it take for the annular temperature to cool
down to a temperature favorable for hydrate formation in the event of a kick?
The primary strength of Presmod can be demonstrated in the solutions to these questions and is
illustrated by Figures 1 thru 3 below.
Figure 13 - 9
Temperature at Start of Drilling
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 13-20