This abstract demonstrates the application of an advance Extra Deep Azimuthal Resistivity tool to efficiently maximize reservoir exposure and map the reservoir architecture in an extended reach well of a mature field. The study shows how to maximise benefit from using advanced geosteering technology to successfully place the horizontal drain in an oil-saturated layer, map the water encroachment and design lower completion accordingly. The reservoir is composed mainly of Grainstone to Packstone, with rock analysis showing highly heterogeneous limestone of good to excellent porosity and permeability. Total thickness is about 30 to 40 ft. with the target zone delineated on the upper part of the layer, within 6 ft of the top. The challenges identified during the pre-well stage are: (1) Oil columns getting thinner as fields become more mature; (2) OWC exhibits less clear-cut boundaries and commonly displayed as transition zone profiles; (3) Resistivities within the transition zone vary along the lateral due either to proximity to other producing wells or to porosity variations within the geology; (4) Low resistivity environment; and (5) The increased uncertainty associated with conventional ‘deep’ resistivity tools to differentiate multiple resistivity layers. The reservoir is under water injection and consequently, water movement is irregular due to the presence of high permeability streaks. There is high risk of water encroachment, which the Conventional ‘Deep’ Resistivity tools with limited depth of detection would not be able to differentiate. Utilizing an Extra Deep Azimuthal Resistivity tool offered a solution to efficiently geosteer the drain within 6 ft. from the top boundary, and map the water saturation around it. A feasibility inversion model incorporating the geological setting of the area and the water encroaching scenario predicted that the Extra Deep Azimuthal Resistivity tool would map the denser top of the target zone, the transition and water encroachment intervals with high confidence at a remote distance from the wellbore. This reduced the uncertainty around well placement so the tool was included in a Triple combo BHA to enable informed and proactive geosteering decision-making process. The long horizontal drain was successfully placed along the porous oil-saturated zone and the water risk was mapped continuously below the wellbore. The Extra Deep Azimuthal Resistivity technology mapped multiple resistivity layers leading to better understanding of the structural model and fluid distribution. The delineation of the resistive dense layer above the wellbore also facilitated good well placement at the required stand-off from the roof. Furthermore, the tool demonstrated its ability to map the top of the transition zone and the resistivity below, which is valuable in identifying intervals where the transition zone was swept with water requiring isolation in the completion. As a direct result, the completion design was optimized to reduce water risk.
Variable reservoir thickness, heterogeneity, and presence of geological truncations are some of the challenges inherent in draining complex reservoirs. These challenges affect the depth of detection of some formation evaluation tools, the ability to optimally place the well in the target horizon, and the ability to remain in the sweet spot throughout the drain length. To mitigate these challenges, reservoir navigation service with fit-for-purpose tools and robust software is required. This paper is a case study of the application of the VisiTrak™ tool and Multi-Component-While-Drilling (MCWD) inversion software (Sviridov et. Al., 2014) in the geosteering of Well-X. VisiTrak is an extra deep-reading azimuthal propagation resistivity tool. MCWD is software that essentially creates a geological earth model from the readings of azimuthal propagation tools. It is multi-layer inversion software. Well-X is located in offshore Niger Delta and the target reservoir consists of several individual turbidite complexes and stacked channels. The successes recorded in this geosteering case include accurate subsurface structural interpretation, reservoir characterization, and achieving well objective in terms of net sand drilled. This paper demonstrates the importance of reservoir navigation in accurate well placement, the benefits fit-for-purpose tools bring to geosteering complex reservoirs in the Niger Delta and shows the value of data integration in reservoir navigation service.
A novel method for the generation of travelling waves in soft robots is presented. Here a soft elastomer membrane is embedded with freely sliding nylon tendons. Instead of being anchored to a point on the membrane, these tendons transmit force via friction generated by sliding within the interior of the membrane. This system can produce continuous travelling waves with amplitudes of 27-45mm at wave speeds of up to 23mm/s, using only a single actuator to apply tension to the tendons. The travelling waves were able to move granular material (poppy seeds) as well as a 147g apple. Experimental results demonstrate that the wave progresses through three phases; the initial static phase, followed by the travelling wave phase and finally the (end of travel) blocked phase, with curvature increasing and wave amplitude decreasing across the travelling and blocked phases. This represents wave degradation in which the membrane compresses relative to the tendon, though this did not limit wave travel over the displacements tested. The wave speeds produced were an order of magnitude higher than tendon winding speed suggesting the system acts with natural gearing. This mechanism shows promise for applications in matter transport of unstructured or soft objects and the principle could also be applied to locomoting robots as the low amount of actuators and degrees of control would reduce the complexity and bulkiness of the robots.
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