Proceedings Volume Cover
OIL MUD LOGGING ON THE GULF COAST  
by H. C. Robinson  
Schlumberger Well Surveying Corporation  
Beaumont, Texas  
ABSTRACT  
Effective logging programs are available for wells drilled with non•  
conductive oil muds. The basic log in such a program is the simultaneously•  
recorded Gamma Ray-Induction Survey. This log provides the primary  
means for correlation, depth control, and for determination of resistivity  
values for qualitative and quantitative interpretation.  
The Sonic Log, used in conjunction with the resistivity values from  
the Induction Log, serves as an excellent detector of hydrocarbon-bearing  
zones.  
Determination of porosity is best accomplished with the Formation  
Density Log. In addition to supplying reliable values of effective porosity,  
this is the most accurate logging means of determining the lithology of the  
sand-shale sequences, found in this area.  
The use of Induction, Sonic, and Formation Density Logs provides  
data for complete interpretation of water saturation, effective porosity,  
and shale content.  
Other wireline tools, such as Neutron, Dipmeter, Sidewall Coring,  
and Wireline Formation Testing, are effective in oil muds.  
OIL MUD LOGGING ON THE GULF COAST  
by H. C. Robinson  
Schlumberger Well Surveying Corp.  
Beaumont, Texas  
Effective logging programs are available for wells drilled with non-conduc-  
tive oil muds. Many of the logs are obtained with the same tools that are  
recommended for water-base mud logging. The interpretation techniques are also  
very similar. However, the fact that such oil muds are not electrically conduc-  
tive requires some variations in both the services run and the interpretation  
methods used.  
During the past year the frequency of drilling with oil muds has increased  
in the area of the upper Texas Gulf Coast. The formations in this area are  
relatively unconsolidated sand and shale series. While many of the points  
covered in this paper are broadly applicable, the examples and discussion are  
based exclusively on experience in this particular area.  
For the purposes of this paper, oil muds are those in which  
a non- conductive  
fluid is the continuous phase. Thus, oil, oil-base, and inverted emulsion muds  
fall into this category. Regular oil emulsion muds, in which water is the con-  
tinuous phase, are not included since such muds will conduct electrical current.  
Basic Log  
The basic log for oil muds is the simultaneously recorded Gamma Ray-Induction  
Log as shown in Figure 1. The role of this particular log is essentially the same  
as that of the Induction-Electrical Survey in water base muds. Correlation, depth  
control, and resistivity measurements for both qualitative and quantitative inter-  
pretation are afforded by this combination log. For correlation, the gamma ray is  
used in liew of the SP, and the induction conductivity curve is an excellent replace-  
ment for the short normal. The Induction Log reliably indicates true formation  
resistivity; there is no conductivity signal from the borehole. Experience in this  
i,  
1
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