Abstract

This paper presents a methodology which allows performing a real time characterization of the conductive natural fractures permeability intercepted by the bit while drilling. Such fractures are detected by monitoring continuously flowing from the wellbore into surrounding formations and the mud losses at the rig-site using flow-meters measuring both the ingoing and the outgoing mud flow.

Moreover, when drilling naturally fractured reservoirs, mud loss data provide one of the most effective means to assess the existence of conductive fractures intercepting the wellbore and therefore to identify potentially producing intervals.

The patterns in the variations of these volumes are analyzed to identify open fractures. The advanced Flowmeter has increased the resolution of the mud flow measurements. It has enabled the authors to assess the flow quantitatively and relate mud flow anomalies with the presence of open fractures down hole in the trial exploratory well.

The mud flow anomalies were validated with surface drilling parameters and gas indications. It was observed that the open fractures were associated with increase in torque and gas indication. The mud flow anomalies also provide crucial information for early kick or losses detection in high pressure gas wells because a better accuracy and a quicker response in detecting kicks and losses can be achieved by monitoring the changes of the mud flow rate by using flow meters measuring the inflow and the outflow mud rate, respectively.

Method and Theory The most commonly used techniques to detect the mud losses consist in monitoring the level of the mud pits with acoustic, floating sensors and/or using paddles set inside the flow line that measure the return mud flow rate with a small degree of accuracy. The traditional Flowmeter provides a simple qualitative fluctuation in mud flow. In contrast this advanced Flowmeter works on the principle of converting mudflow out in to an analog signal which represents the volume of mud.

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