The Effects of Weight Material Type and Mud Formulation on Penetration Rate Using Invert Oil Systems
- J.P. Rupert (NL Baroid/NL Industries, Inc.) | C.W. Padro (NL Baroid/NL Industries, Inc.) | S.R. Blattel (NL Baroid/NL Industries, Inc.)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 4-7 October, San Antonio, Texas
- Publication Date
- Document Type
- Conference Paper
- 1981. Society of Petroleum Engineers
- 1.2.3 Rock properties, 1.6 Drilling Operations, 1.11 Drilling Fluids and Materials, 1.5 Drill Bits, 1.11.4 Solids Control, 2.2.3 Fluid Loss Control, 5.8.2 Shale Gas, 1.5.4 Bit hydraulics, 4.3.4 Scale, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.15 Fundamental Research in Drilling
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The penetration rates of invert oil mud systems in Mancos Shale have been measured using the full-scale wellbore simulator at the Drilling Research Laboratory. Experimental parameters were 1.) weight material type - high specific gravity (ilmenite) vs conventional (barite); 2.) fluid formulation - low colloid type (relaxed filtrate) vs conventional (low filtrate) and 3.) bit type - synthetic diamond insert blank vs conventional (three-cone roller). In addition to laboratory data, field case history data for corresponding systems have been studied. Maximum penetration rates were observed for the minimum solids system, especially when used in conjunction with the synthetic diamond insert bit.
The relative advantages and disadvantages of drilling with oil-based drilling fluids are widely recognized. By comparison with water-based fluids, invert emulsion oil muds provide maximum wellbore stability, improved thermal stability, excellent tolerance to contaminants, i.e., hydrogen sulfide, carbon dioxide and salt water, and are relatively easy to maintain. On the other hand, oil muds have a relatively high initial cost. In addition, there is increasing concern for the environmental considerations attendant with the use of oil muds, especially with the sale and non-polluting disposal of the muds and cuttings obtained during their use.
While invert oil muds can provide reasonable penetration rates in most situations, they have penetration rates in most situations, they have provided notoriously slow rates in deep provided notoriously slow rates in deep low- permeability formations.
In recent months, considerable attention has been given in the drilling industry to the use of low colloid invert oil mud formulations as a means of providing increased drilling rates. In these systems, the inclusion of colloidal material (including micro-emulsion droplets) is held to a minimum. A corresponding increase in fluid loss is observed in these systems, concomitant with the minimal inclusion of colloidal fluid loss control additives.
In addition, the drilling industry has also seen the introduction of several other developments in drilling fluids technology, specifically the advent and application of relatively high specific gravity weight materials such as ilmenite and hematite, and the introduction and use of the synthetic diamond insert blank.
Rationale indicates that both of these developments should provide for increased penetration rates, in the former case because of reduced total solids in the drilling fluid, and, in the latter case, because of the biting action of the insert with concurrent longevity of service.
This paper describes tests performed employing a full-scale wellbore simulator which document the effects of variations in weight material type, mud formulation and bit type on the penetration rates in shale cores of extremely low permeability.
STATEMENT OF THEORY AND DEFINITIONS
The factors influencing the in situ penetration rate of a bit in a formation are numerous, penetration rate of a bit in a formation are numerous, and have been the subject of numerous dissertations. In general, the factors that affect penetration rate are the following:
- Drill Bit - Weight on Bit - Rotary Speed - Mud Hydraulics - Mud Properties
In addition to those dependencies noted above, it has been empirically determined that the total solids content of the fluid exercises a profound influence on penetration rate.
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