This work describes a 3D approach that was used to reduce drilling risks and unscheduled events in Palo Azul field. The field is in the Oriente foreland basin (Figure 1), contiguous to the Ecuadorian Andean foothills. A portion of the field presented an unexpected igneous intrusion (laccolite) just above the reservoir formation. The 3D analysis combined 3D seismic information with the 3D structural and geological model to generate a 3D geomechanical model. The mechanical earth model (MEM), relied on onsite real-time monitoring, was used to support drilling decisions, providing predictions of well trajectory, casing points, and mud window. The 3D velocity/amplitude cube, derived from one portion of the 3D seismic program, was used as the base to construct the MEM. To capture the uncommon structural characteristics associated with the complex geological structure, an innovative methodology was developed. Steps included special reprocessing of sequences of the seismic data; structural model reinterpretation; 3D seismic velocity analysis; population of the rock properties in the 3D domain (Geostatistical approach); integration with wireline logs; core measurements analysis; and drilling history review of the offset wells. The real-time geomechanics support allowed making important decisions in time when unplanned events occurred while drilling. This new methodology created a systematic approach to well planning that reduces drilling risks in the development of a complex area. The value added by the integrated team's efforts was demonstrated by drilling the next two wells with significant reductions in costs and nonproductive time. A sensitivity analysis of different well trajectories across fractured zones was performed. Wellbore stability forecasts were compared with reference to the 3D model developed. The results obtained contribute to a better understanding of the mechanics of stress development around a magmatic intrusion and a faulted/folded zone. The methodology developed allows better insight into the parameters that must be included in the 3D MEM creation and wellbore stability forecast for similar environments. This method also serves as a good basis for further development, such as sanding studies, completion design optimization, reservoir studies, and uncertainty analysis. Introduction Palo Azul field, operated by Petrobras Energia Ecuador, is a development field located in the Oriente Basin. This field is being developed by three different well pads.During the planning stage of well PA-14, Petrobras Energia identified the risks in this area, based on an unsuccessful experience during drilling one well into this dome structure formed by igneous intrusion. The Geomechanics group from Schlumberger, integrated with the Drilling and G&G group from Petrobras Energia, developed a 3D solution that minimizes the drilling risks in this area. RockSolid[TM], wellbore stability software[1], was used to construc a 1D MEM (Mechanical Earth Model) [2], which was calibrated through drilling events analysis, image logs, and core-strength data from multistage triaxial test. The mechanical earth model is a numerical representation of the state of stress and rock mechanical properties for a specific stratigraphic section in a field or basin. Petrel[TM], 3D geological modeling software[3], used this information in conjuction with an acquired vertical seismic profile (VSP) and 3D seismic, to build the 3D-MEM. This new model uses a basic petrophysical and sonic well log curves to determine the mechanical properties. Using the available geostatistical tools, these mechanical rock properties were populated across the field. The geological and structural model previously defined in Petrel[TM] was taken into account followed by the use of the 3D seismic velocity cube. The advantage of this method is that it can handle several parameters using a 3D approach to design the optimal well trajectory.In this work, the sensitivity of well trajectory across the fracture zones, mainly limestone layers, were investigated. The sensitivity analysis is performed for several well trajectories; following velocity anomalies related to these fracture zones in combination with structural features.

Casing drilling technology uses a specially designed casing drill bit that is attached to a traditional casing string. The technology is typically applied when hole problems such as severe formation swelling or caving cannot be controlled with drilling mud or by rig operations, making it extremely difficult to reach the planned casing setting depth. In these applications, the casing and bit are set and cemented. To drill the next section of the wellbore, the casing drill bit, as well as the float equipment, must be drilled out. In PDC bit applications this is typically done in two ways – using a roller cone bit for the drill out, followed by a new PDC bit for the next interval; or by using a single new PDC bit and BHA to drill out the cemented casing bit and continue drilling the next interval. Each method presents inherent inefficiencies in the drilling operation. With the first, additional drilling and trip time are required to run the two bits. The second method using a single new bit has the potential to damage the PDC cutters while drilling out the casing bit such that performance is limited in the next formation interval. The cutter damage is heightened when using a bent motor assembly. This degraded cutter condition negatively affects bit durability and performance, resulting in slower rates of penetration, shorter runs, and pulling the bit before completing the intended interval. Milling cap technology has been developed for the single-bit method that provides a shearing action during the casing bit drill out process while protecting the primary PDC face cutters. It preserves the cutters in virtually pristine condition so that performance is optimized when drilling the formation. The shearing cap technology allows flexibility in selecting the best performing bit for the interval below the casing, and it increases the opportunity to use a bent motor assembly when drill string rotation is required during the drill out. This paper discusses the development of the shearing cap technology and examines the two initial field tests in South America and West Africa. In the first use of the technology, drilling on a well in Colombia, an 8 ¾-in. PDC drill-out bit with shearing caps completed the drill out portion of the run in less than 15 minutes. The bit then drilled the next 4,900 foot formation interval to the next casing point with an ROP 5% higher than the field average. The bit showed no signs of reduced ROP after the drill out and came out of the hole in good condition with a dull grade of 1-2-CT-G-X-I-BT-BHA. In West Africa, a 12 ¼-in. PDC bit with shearing caps produced the best performance in the field, reducing casing bit drill out time by 44% and improving ROP in the formation by 50% compared to offsets.