Abstract
Drilling deep gas wells poses a set of significant technical challenges, many of which approach or push the boundaries of equipment operational limits. The need for formation evaluation data in the deep gas reservoirs can be explained by the fact that relatively little is known about these reservoirs as data acquisition has been previously limited by temperature, pressure and hole size limitations of the instrumentation in older WL and LWD tools. Well bores of 5 in. or less may prohibit conventional logging-while-drilling (LWD) tools from acquiring necessary data. In addition, the consequences that high pressure has on mud systems which cause LWD and MWD data pulses to be compromised. Because standard LWD equipment had experienced numerous failures at such difficult down hole conditions, a new class of LWD and imaging tools was developed to address this challenging situation, This new class of tools opens new possibilities for data acquisition and evaluation in deep gas reservoirs. The paper will discuss:
What technology exists today?
The challenges in developing these technologies?
The advantages and limitations of the technology.
The measurements that will bring benefit in understanding the reservoirs such as real time imaging for fracture ID, (fracturing is a critical component as these reservoirs are rather tight and require natural or induced fracturing to enhance the permeability) The features and capabilities of the new tools will be discussed in this paper together with a brief introduction of few case studies representing the hot drilling in the North Sea, the heavy mud in China and the successful acquisition of high-quality data in a deep and slim hole well in Italy.
