Summary
Filter-cake characterization is very important in drilling and completion
operations. The homogeneity of the filter cake affects the properties of the
filtration process such as the volume of filtrate, the thickness of the filter
cake, and the best method to remove it. Various models were used to determine
the thickness and permeability of the filter cake. Most of these models assumed
that the filter cake was homogeneous. The present study shows that the filter
cake is not homogeneous, and consists of two layers of different
properties.
The objective of this study is to measure the filter-cake thickness and
permeability of water-based drilling fluids by a new approach and compare the
results with previous models. A high-pressure/high-temperature (HP/HT) filter
press was used to perform the filtration process under static conditions (225°F
and 300 psi). A computed-tomography (CT) scan was used to measure the thickness
and porosity of the filter cake. Scanning electron microscopy (SEM) was used to
provide the morphology of the filter cake.
The results obtained from the CT scan showed that the filter cake was
heterogeneous and contained two layers with different properties under static
and dynamic conditions. Under static conditions, the layer close to the rock
surface had a 0.06-in. thickness, 10- to 20-vol% porosity, and 0.087-µd
permeability, while under dynamic conditions, this layer had a 0.04-in.
thickness, 15-vol% porosity, and 0.068-µd permeability. The layer close to the
drilling fluid had a 0.1-in. and 0.07-in. thickness under static and dynamic
conditions, respectively, and it had zero porosity and permeability after 30
minutes under static and dynamic conditions. SEM results showed that the two
layers contained large and small particles, but there was extremely poor
sorting in the layer, that was close to the drilling fluid, which led to zero
porosity in this layer. Previous models underestimated the thickness of the
filter cake by almost 50%. A new method was developed to measure the thickness
of the filter cake, and various models were screened to identify the best model
that can predict our permeability measurements.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
4 August 2011
- Meeting paper published:
8 June 2011
- Revised manuscript received:
23 February 2012
- Manuscript approved:
28 February 2012
- Published online:
1 June 2012
- Version of record:
11 June 2012
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