Mud logging services provide detailed information regarding the lithology and fluid content of rock samples circulated to the surface in drilling fluid during the drilling of oil and gas wells. Other measured parameters include rate of penetration, pump rate, pump pressure, weight on bit, strokes per minute, mud weight, mud viscosity, and mud volume. The lithology is interpreted by personnel working in a mobile laboratory at the well site by examining rock cuttings, and the other parameters are measured by equipment on the rig or in the mud-logging unit. In most instances, mud-logging is performed by third parties contracted by the drilling operator.
It is important to identify your objectives before selecting potential mud loggers. There are different levels of evaluation required depending on project specifics, which will determine the sophistication of personnel and equipment needed. When drilling development wells in an existing oil and gas field, it is common practice for mud loggers to utilize a basic gas detection system. The drilling of exploratory, or wildcat, wells requires more sophisticated gas chromatography equipment and pore pressure analysis.
It is important to know the experience levels and the background of potential contract personnel. This includes both overall experience and experience in a specific geologic area. It is extremely important to select mud loggers with extensive experience when drilling exploratory wells or wells that are being drilled in an overpressured environment. When drilling in areas where lithology description and formation identification are the primary objectives, it is imperative to select mud loggers with substantial local expertise.
Equipment that is not operating properly will produce invalid data, which will result in bad decision-making. The most common equipment used by mud loggers is the gas chromatograph. If not calibrated correctly, false readings can result in the misinterpretation of the amount of gas in the drilling fluid system. This could create a dangerous work environment with potentially catastrophic consequences.
It is imperative to integrate and utilize the data and interpretation provided by the mud-logging consultant. The services provided by the mud-logger are real time, as opposed to pre-drill data used to develop the initial drilling program for a well. Adjustments to the drilling plan are often necessary based on data gathered by the mud-logger during the drilling of a well.
Pay attention to your goals and objectives before deciding the level of service required. When drilling in a normally pressured environment, basic services such as gas monitoring, rate of penetration, and lithology description might be all that are required, resulting in significant savings.
Cost alone shouldn’t be the determining factor in selecting the appropriate mud logging consultant. It might be better to spend more for services when drilling in areas of complex geology or in high-pressure environments. In these situations, additional specialized equipment and additional personnel might be appropriate.
Disregarding data or recommendations from your mud loggers can create dangerous situations and result in missed opportunities. Mud loggers are the first-line of defense in identifying conditions at the wellsite that can potentially cause a well blowout. In addition, mud loggers can identify zones of interest for possible oil and gas production that might be overlooked by geoscientists using other available data.
There are many providers of mud-logging services available to companies drilling for oil and gas. Some concentrate on working offshore while others work strictly onshore. In addition, some providers focus on areas exhibiting extreme pressure conditions requiring expensive, sophisticated equipment and very experienced personnel.
There are many mud logging consultants to choose from and the process of selecting the best one for your particular situation can seem daunting. By focusing on what you are trying to accomplish at the beginning of the selection process, you can identify the best service provider for your specific needs.
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