This reference is for an abstract only. A full paper was not submitted for this conference.
The drilling of horizontal and multilateral wells has grown rapidly over the last decade. Successful geosteering of these wells in thin reservoir layers requires an accurate reservoir model that is updated in real-time with incoming logging-while-drilling (LWD) data. 3D geological modeling-while-drilling workflows, which utilize geostatistical techniques, were developed to facilitate model updating, while improving the accuracy and reducing the cycle-time of the geosteering process. A data link between LWD tools in the field and Saudi Aramco's offices in Dhahran provides real-time information to quickly update the 3D earth model, enabling multi-disciplinary geosteering teams to make fairly quick decisions regarding well bore trajectory changes.
In the initial step of the modeling-while-drilling workflow, a sector model which includes the planned horizontal well and neighboring wells is extracted from the existing full-field 3D geological model. Downscaling is applied to generate a fine resolution model along the planned well path. Using nearby welldata, the model is subsequently populated with reservoir properties such as porosity and gamma ray by means of variograms and geostatistical techniques, for instance Kriging or Sequential Gaussian Simulation (SGS). Pseudo well logs could be extracted along the planned well path for comparison with LWD measurements.
The 3D earth model is continuously updated during the drilling phase by automatically loading and integrating LWD data transmitted from the field. Quick model updating is done both for the structural and petrophysical components of the model. The new well data and revised earth model are analyzed in real-time, allowing the multi-disciplinary geosteering team to quickly make changes to the planned well path and convey those changes to the drilling engineer at the rig.
Field examples in various geological settings will be used to illustrate the modeling-while-drilling approach. It is an extremely useful technique that can be utilized to optimize well path, maximize well productivity, and reduce rigwait time. In addition, it allows professionals from different disciplines, whether in the field or geosciences centers, to work together in an integrated manner so as to reduce costs and improve well placement.