BAKER HUGHES - Drilling Fluids Reference Manual

TABLE OF CONTENTS
represented diagrammatically in the figure above. Presuming there are no other “helper” gases to
promote hydrate formation, then the lower molecular weight of the hydrocarbon, the greater the
resistance to hydrate formation. Thus the hydrate formation is decreased in the following order:
Methane < Ethane < Propane < Isobutane
The cold sections of the well that are exposed to the sea such as the riser, choke & kill lines and the
BOP are the most probable location for the hydrates formation. When the drilling fluid is being
circulated, the combination of heat generated from the actual circulating and the geothermal heat will
maintain the temperature of the fluid in the riser above the critical temperature at which hydrates are
formed. However when there are circulation breaks for tripping or logging, the drilling fluid must
have the hydrate inhibitive capacity to keep the fluid in the cold areas of the well hydrate free.
Invert emulsion drilling fluids, which are very commonly used on deepwater drilling operations, are
extremely effective hydrate inhibitors. They are not hydrate preventers, as hydrates may be formed
given the right pressure-temperature-water content-calcium chloride concentration combination.
HYDRATES PREDICTION
The WHyP (Westport Hydrate Prediction) program used by Baker Hughes Drilling Fluids is a
thermodynamic hydrate equilibrium prediction program that is based upon the statistical
thermodynamic theory of van der Waals and Platteeuw. It also incorporates the hydrate temperature
suppression methods developed using the Young-Yousif model.
The WHyP program has a wide array of input choices and modes that can be used. The design mode
is a unique feature that calculates the appropriate amount of inhibitor to suppress hydrates at a given
temperature and pressure. The prediction mode allows the user to enter a fluid composition and the
program will generate the hydrate equilibrium line for that particular fluid. Characterizing this fluid
composition can be completed in a number of ways; by weight percentage, by filtrate density and
resistivity, and measured water activity. The program will predict hydrate equilibrium curves up to
10,000 psi.
The WHyP program was designed by, and for, drilling fluids personnel and caters towards deepwater
applications. Fluids with up to three different types of inhibitors may be entered as inputs. The
program also has a wide array of inhibitor selections, such as NaCl, KCl, CaCl 2 , Sodium and
Potassium Formates, Methanol, and several types of glycols. The program defaults to using Green
Canyon Gas, but also allows the user to enter a known gas composition.
Although based upon statistical models, the WHyP program is supported by over 150 temperature
suppression points that were measured experimentally on various mixed salts and glycols solutions.
This large supporting database allows WHyP to be accurate as well as flexible to the needs of the
drilling fluids personnel. The WHyP program is accurate to within 2K psi when using the weight
percentage method, or 4K psi by using the filtrate or water activity methods.
Baker Hughes Baker Hughes Drilling Fluids has been using WHyP to assist with the design of
hydrate inhibiting fluids since 1997 . The program’s mixed salt/glycol capability differentiate it from
other hydrate prediction programs.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 13-15