David Hinz

Deepwater hazard avoidance in a large top-hole section using LWD acoustic data

Drilling expensive and challenging wells in deepwater requires significant prewell planning to mitigate risks. Understanding the regional drilling hazards that nearby operators have encountered and correlating them to the current project must be done to gain a clear appreciation of potential problem hole sections. This paper describes a deepwater well drilled by Agip where significant efforts were taken to fully evaluate the potential for a shallow water flow in the top-hole section. Another operator in a nearby block had recently lost well to a shallow water flow. This heightened the concern of the Agip asset team so an extensive pore-pressure analysis of the surface seismic data was undertaken. The results of this analysis indicated that there was also a strong potential for a shallow water flow on this well. In order to build the best possible understanding of the pore pressure profile the surface seismic pressure analysis was taken much deeper than what is customary, in this case to the top of the salt. Prewell pore pressure models confirmed Agips surface seismic pore pressure assessment. As a result, real-time pore pressure monitoring services were deemed essential to closely monitor the progress of the well and, with that information, make real-time adjustments to the drilling parameters (i.e. mud weight) as they became necessary. An extremely important and sometimes overlooked aspect of real-time interactivity is the definition of the role each team member has and how each team member interacts with the others. Assembling a team and defining each members roles and responsibilities in the planning phase streamlines the time-critical decision-making process and allows for a decisive, unambiguous, work flowpath. Figure 1 shows the communication and workflow organization assigned by Agip before the well was drilled. Rig-based personnel are highlighted in green and office-based personnel in blue. The operations geologist was the …

Azimuthal Gamma Images Uncover Stratigraphic Features in a Seemingly Featureless Unconventional Reservoir

This paper discusses the benefits of using an azimuthal gamma ray tool for wellbore placement to better understand the stratigraphy of the formation. The use of real-time azimuthal gamma images made it possible to determine if the wellbore was moving up or down stratigraphically. Importing the images to borehole imaging software allowed for the calculation of borehole dips and true dips (resulting in a more accurate correlation) dip calculation of the Middle Bakken surfaces, and a better understanding of the stratigraphy surrounding the borehole. A comparison was established with laterolog resistivity images from the same area that were of higher resolution and higher cost, validating the use of azimuthal gamma for dip calculation. The azimuthal gamma ray measurement provides insight into stratigraphic well placement beyond what can be determined from bulk average gamma ray. Data acquired from the gamma ray image can help to further refine geosteering decisions and reduce uncertainty in wellbore placement.