THE EFFECTS OF GEL STRENGHT ON THE OVERALL PERFOMANCE

OF DRILLING FLUID

SEMINAR PRESENTATION

BY

ALADETAN FELIX.I

CONTENTS

• CONTENTS• INTRODUCTION• WHAT IS GEL STRENGHT• TYPES OF GEL STRENGHT AND HOW IT IS MEASURED• FACTORS THAT AFFECT GEL STRENGHT IN WBM

AND OBM• EFFECTS OF EXCESSIVE AND WEAK GEL STRENGHT• TREATMENTS AND IMPORTANCE OF GEL STRENGHT• CONCLUSION

INTRODUCTION

A proper drilling fluid is designed based on the requirement of the application In which it will be used. Its properties directly relates to its function. The desired properties must be understood and routinely evaluated throughTesting.A series of measurement are taken to test for this properties so as to obtainCrucial information about the performance of the drilling fluid.One of such information is the cutting carrying capacity of the fluid whichDefines the Gel Strength of the fluid.The Gel Strength is one property that involves both measurement andFurther evaluation to fully understand and derive maximum benefit fromIts use.It’s a rheological measurement taken with a viscometer after varying Lengths Of static condition.

WHAT IS GEL STRENGHT?Gel strength is the shear stress of drilling mud that is measured at low shear rate after the drilling mud is static for a certain period of time. The gel strength is one of the most important drilling fluid properties because it demonstrates the ability of the drilling mud to suspend drill solid and weighting material when circulation is ceased.Its important in all drilling fluid industries as many fluids are thixotropic (time dependent). As the fluid remain static or un agitated especially during connections and operational down time, it begins to gel. This gelling aid the suspension of cuttings while fluid motion is stopped.A drilling fluid must be capable of effective cutting transport under dynamic conditions and appropriate but not excessive suspension under static condition.

HOW CAN WE MEASURE GEL STRENGTH?

We use the 3-rpm reading which will be recorded after stirring

the drilling fluid at 600 rpm from a rheometer. Normally, the first

reading is noted after the mud is in a static condition for 10

second. The second reading and the third reading will be 10

minuets and 30 minutes, respectively. You may wonder why we

need to record the 3-rpm reading after 30 minutes.

The reason is that the 30 minute-reading will tell us whether the mud

will greatly form the gel during an extensive static period or not. If the

mud has the high gel strength, it will create high pump pressure in

order to break circulation after the mud is static for long time.

Furthermore, increasing in a trend of 30-minute gel strength indicates a

build up of ultra fine solid. Therefore, the mud must be treated by

adding chemicals or diluting with fresh base fluid.

The 10sgel reading approximate the true yield stress for most systems.

TYPES OF GEL STRENGHT AND HOW IT IS MEASURED

• Depending on the time it takes to gel, we have three types of gel strength namely:

• The high flat gel• The progressive and• The low flat gel (most desirable)Depending on the range between 10s and 10mins gel reading. The range or difference is significantly high for both the high and progressive gel, and it indicate rheological troubles for the mud .but there is no real difference for that of the low flat gel. The magnitude of gelation with time is a key factor in mud and it should not be too high to suspend cuttings and weighted materials.

FACTORS THAT AFFECT GEL STRENGHT

WATER BASED MUD

• Bacteria• Drill solid• Salt• Chemical contamination as

lime, gypsum, cement, and

anhydrite• Acid gases as Carbon

Dioxide, and Hydrogen Sulphide

OIL BASED MUD

• Over treatment with organic gelling material

• • Build up of fine solid particles in the mud

EFFECTS OF EXCESSIVE AND WEAK GEL STRENGHT AND TREATMENT

EXCESSIVE GEL STRENGHT• Swabbing • Surging • Difficulty in getting logging tools to

the bottom• Retaining entrapped gas, cuttings

and sand while drilling• Increase in gel strength is always

equals increase in YP• Loss of fluids down hole• Formation matrix can be damage

while attempting to free stuck pipe.• Increased ROP and high pumping

pressure that may break formation and result n loss circulation issues

WEAK GEL STRENGHT• Inadequate cutting suspension

ability• Build up of cutting bed with the

bore path tending to stuck pipe• Poor hole cleaning• Contamination problems• Barite sag

TREATMENT AND IMPORTANCE OF GEL STRENGHT

1.Dilution: this is the simplest method for lowering solid concentration. Keep total mud volume as small as practical and dump as much mud as possible before each dilution.2.Mechanical separation: screening and applied g force settling are the two most commonly used.3.Chemical – Mechanical separation: the use of both chemical and

screening devices and\ or g- force (chemical flocculation and dewatering)

IMPORTANCEThe major advantage of a good gel strength is its cuttings suspension ability which will provide a good hole cleaning process.

CONCLUSION

It is obvious from the above information that a good low flat gel strength is as important as a well formulated drilling fluid. They say solid is the mud engineer's greatest enemy, looking at the varieties of problems associated with high solids concentration, like a wise teacher once said ‘it is better to avoid high solid concentration than to know all the treatment techniques’.

Thank You