The Horizontal Automated Wing Drilling Equipment (HAWDE) machine is an enabling technology for automated drilling of large aircraft parts. HAWDE is a five axis drilling machine that operates over the upper and lower surfaces of eight wings, each more than 40 meters long and four stories tall. The machine accesses the entire A380 wing using a combination of elevators and a machine transporter that carries the machine from surface to surface. HAWDE drills holes in spars, butt splices, and rib feet in the wing box final assembly jigs for A380.
The objective of this paper is focused on presenting and highlighting the results of the first successful reservoir fluid characterization and sampling attempt in offshore Abu Dhabi and the added values to the assets operating in the highly heterogeneous Jurassic carbonate reservoirs with unknown formation water salinity values. The original formation water has a unique high salinity that got mixed overtime with the fresher injection water, so that the open hole log interpretation using Archie water saturation model becomes highly uncertain. Exaggerated oil saturations could be computed within the water zones around the oil-water contact. In addition to measuring the fluid mobility, the formation testers are being run to confirm the fluid type present in the reservoir by using pressure gradient plot or by fluid identification and sampling stations. The increasing cost and rig time optimization demands inspired the team to utilize the emerging formation sampling and testing while drilling at the first time in offshore Abu Dhabi to replace the conventional wireline/ drill pipe conveyed formation testers. This application proved to be an added value to gather the required reservoir data in a mature challenging field reducing the operational time, cost and associated risks. A water injection well is drilled across a highly heterogeneous, Jurassic carbonate reservoir offshore Abu Dhabi. A deviated pilot hole was drilled for formation evaluation and reservoir fluid assessment, and the plan was to continue with a horizontal drain into one of the sub-reservoirs (swept area) if confirmed water bearing. The logging while drilling formation sampling and pressure testing tool was run combined with the conventional open hole logs to minimize the formation exposure time, real time down-hole fluid analysis started very shortly after drilling to the bottom of the target reservoir, based on the rush open hole log interpretation. Different sensors, with different physics (namely; fluid viscosity, density, sound speed, optical refractive index, temperature, fluid mobility and compressibility) were used to characterize the fluid during the pump-out stations. Due to the minimized mud filtrate invasion effects, this operational sequence allowed the gathering of conclusive formation fluid samples with less pumping time and volume. This paper shows the operational planning, design and execution outlines, discusses the benefits of acquiring clean formation samples right after drilling compared to those acquired with the conventional conveyance techniques, and indicates the drawbacks and the limitations of this technology together with any window of improvement.
The development of Lower Cretaceous reservoirs in a mature field located 84 km southwest of Abu Dhabi required a series of stress measurements across the reservoirs to tectonically calibrate the 3D Geomechanical model. The stress measurements were acquired by multiple straddle packer microfrac tests conducted through pipe-conveyance in a slim openhole wellbore. Various pore pressure depletion conditions across the reservoirs make the deployment of straddle packer tools in slimholes a very challenging operation. Five in-situ stress measurements are acquired in this study from the proper identification of fracture closure pressure after reaching the formation breakdown pressure. Each microfrac test consists of three pressurization cycles and three pressure decline (fall-off) periods after fracture propagation. The fracture closure identification is achieved using three different pressure decline analysis methods on each fall-off test: (i) square-root of time, (ii) G-function and (iii) Log-Log plot. The final fracture closure measurement is obtained after consolidating the three fracture closure identification results in all three injection cycles conducted on each microfrac station. The Microfrac tests conducted in the vertical pilot borehole provide precise in-situ measurements of formation breakdown, fracture reopening, propagation and closure at multiple reservoir layers. These in-situ measurements provide an accurate present-day stress profile across the reservoirs for constructing a proper 3D geomechanical model of the field. These microfrac tests measure minimum horizontal stress gradients of approximately 0.66 to 0.76 psi/ft, confirming the normal faulting stress regime in these reservoirs. The tectonic stress calibration is obtained by adjusting the value of tectonic strains across the reservoirs until the log-derived minimum horizontal stress matches the fracture closure pressure from the microfrac tests. These in-situ stress measurements provide the subsurface information required to fully calibrate the tectonic stress acting on the reservoirs. This tectonic stress calibration is needed to create a representative 3D geomechanical subsurface model to predict accurate subsurface responses to stress and fluid flow over the field development. Additionally, conducting microfrac tests in slimholes provides multiple acquisition benefits: the straddle packer tool tolerates higher differential pressure across the elements than in large borehole, achieving higher absolute bottom hole pressure to induce formation breakdown; the borehole induced stress zone is radially smaller compared to larger hole sizes; the induced fracture does not required excessive propagation away from the borehole in order to capture the far-field in-situ closure stress.
Geomechanical modeling is important to understand in-situ stresses, reservoir stress path, stress contrast, wellbore stability, solid production, integrity of cap-rock and drilling vertical and horizontal wells. The knowledge of the in-situ stresses is critical for pre-drill and post-drill well planning as well as wellbore stability prediction and is needed throughout the life of a well. The uncertainty associated with this geomechanical modeling can be critical and costly if these uncertainties are not mitigated and, to reduce this uncertainty, it is important to have a calibrated geomechanical model. One important technology that can help with reducing the uncertainty is the wireline straddle-packer microfrac tests for in-situ stress characterization. It is an important technology that helps in the measurement of in-situ formation breakdown pressure, fracture propagation pressure and fracture closure pressure. It also helps with other important hydraulic fracturing design such as fracture containment assessment, horizontal stress profile and stress contrast to stimulate tight formation shale gas or oil, water disposal wells and for OBM cutting reinjection wells. The microfrac testing procedure uses the pressure response measured during formation breakdown, fracture propagation, fracture reopening cycles and pressure fall-off cycles for overall stress measurement and fracture closure identification. The objective of this microfrac testing was to validate and calibrate the horizontal stress profile in various intervals of the target formations. This paper focuses on the microfrac testing methodology, the geomechanical principles governing the testing, the resulting interpretation and the geomechanical modeling for horizontal stress calibration in a vertical borehole onshore Abu Dhabi.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.