Geodip – K M Geoscience Ltd, geological consultants, measurement of geological dip, Aberdeen Scotland

Oil and gas wells have been logged with dipmeters since 1965. Early readings were taken from 3 resistivity pads and dip was calculated by hand. The tools were quickly developed to run continuously and more pads were added. Today many tools have almost complete borehole coverage, the technology having converged with borehole imaging tools. Many of the tools measure resitivity at various depths of investigation. Sonic based imaging tools can also be used to measure dips and are particularly good for fracture detection and are not affected by oil-based muds. Recently, it has been possible to run tools in the LWD (logging while drilling) string and transmit images back to surface in real time. Quite remarkable technology.

Interpretation

The early manual interpretation by the dedicated geologist moved into a phase of automated interpretation. While this may be useful for structural dip at the wellsite, much information was lost during the oversimplified automation process. In fact artefacts could be introduced by incorrect processing parameters. Imagine going out into the field, looking at some structures in a cliff and attempting to automate the thinking process. Things have come full circle, for many years dips have been picked by a geologist using special software. The dips are often classified into structural, faults and sedimentological, depending on the resolution and quality of the data, can be further classified into more types.

Linear or Curved Features across the borehole

The most common method is to assume that the beds or features are planar and this is used as a first pass when fitting a sinusoid to the log data. It is in general suitable for shaley sequences of low energy. However, it is also possible to identify curved features such as high energy cross-bedding. Nodules often have curved sides. To define a curved feature, at least a 6-arm dipmeter tool is needed in practice. This gives enough data points to define a curved surface.




			Home Geological Modelling Purpose of Models Sources of Information Working Practices Steps in Geological Modelling Structural Definition Reservoir Layering & Facies Types Petrophysical Modelling Slideshow of Steps Dip in Subsurface Structure in Outcrop Measurement of Dips Scale of Dip Mapping Dips Dip in Cross Section Downloads Rescue Tools Geological Consulting Dipmeters in the Oil Industry Oil and gas wells have been logged with dipmeters since 1965. Early readings were taken from 3 resistivity pads and dip was calculated by hand. The tools were quickly developed to run continuously and more pads were added. Today many tools have almost complete borehole coverage, the technology having converged with borehole imaging tools. Many of the tools measure resitivity at various depths of investigation. Sonic based imaging tools can also be used to measure dips and are particularly good for fracture detection and are not affected by oil-based muds. Recently, it has been possible to run tools in the LWD (logging while drilling) string and transmit images back to surface in real time. Quite remarkable technology. Interpretation The early manual interpretation by the dedicated geologist moved into a phase of automated interpretation. While this may be useful for structural dip at the wellsite, much information was lost during the oversimplified automation process. In fact artefacts could be introduced by incorrect processing parameters. Imagine going out into the field, looking at some structures in a cliff and attempting to automate the thinking process. Things have come full circle, for many years dips have been picked by a geologist using special software. The dips are often classified into structural, faults and sedimentological, depending on the resolution and quality of the data, can be further classified into more types. Linear or Curved Features across the borehole The most common method is to assume that the beds or features are planar and this is used as a first pass when fitting a sinusoid to the log data. It is in general suitable for shaley sequences of low energy. However, it is also possible to identify curved features such as high energy cross-bedding. Nodules often have curved sides. To define a curved feature, at least a 6-arm dipmeter tool is needed in practice. This gives enough data points to define a curved surface.