Abstract

Mudlogging has long been a mainstay within the drilling industry. Historically it has provided the first indication of the presence of liquid and gas hydrocarbons in a wellbore as well as the lithology. If a full suite of wireline logs could not be obtained, it has been the only record of the formations and hydrocarbons present. With the advent and development of horizontal drilling, the value of mudlogging became even more important in assisting, in real-time, with the identification of the relative location of the wellbore within the intended target zone. In the early years of horizontal drilling, the work of the mudlogger and the directional driller provided the only indication that the plans of the operator were being met. As horizontal drilling matured, other methods were added to provide even more information on the location of the lateral. The first of these techniques was computer-based analysis of geosteering that coupled directional drilling mathematical techniques with a comparison of geologic data from the borehole to that of an offset well. As the techniques were refined and more sophisticated software was developed to provide additional tools to assist with the geosteering process, the cost of horizontal drilling decreased and the resulting productivity of the wells increased. The role of the mudlogger continued to be important as ever, since they were still the first to see the rocks and hydrocarbons. Working in tandem with the geosteerer, a much clearer picture of the lateral emerged.

Recent enhancements in the logging industry have improved the mudlogging service in terms of formation evaluation from both quantitative gas analysis and hydrocarbon-fluorescence spectroscopy. These processes provide a level of analysis that supplies extremely valuable data while drilling. All this new information can be given to producers in a standard log format along with other logging parameters.

Well site geochemistry is another technology that can add a tremendous amount of valuable information concerning the drilling of a horizontal well. For example, a few analytical techniques that can be applied that define specific exploration needs are:

1. Plot extractable oil to identify high-liquid hydrocarbons;

2. Provide a direct permeability indicator;

3. Plot gas quality and gas-water contact;

4. Hydrocarbon “finger-printing;” and

5. Precise rock typing.

Each of these services can provide a wealth of data to assist with drilling a horizontal well. However, when combined, producers can realize even great returns from a project, including a savings in time which relates to cheaper drilling costs and with valuable data about the reservoir for both current and future development.