Scientific ocean drilling’s first in situ stress measurement was made at Site C0009A during Integrated Ocean Drilling Program (IODP) Expedition 319 as part of Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) Stage 2. The Modular Formation Dynamics Tester (MDT, Schlumberger)wireline logging tool was deployed in riser Hole C0009A to measure in situ formation pore pressure, formation permeability (often reported as mobility=permeability/viscosity), and the least principal stress (S3) at several isolated depths (Saffer et al., 2009; Expedition 319 Scientists, 2010). The importance of in situ stress measurements is not only for scientific interests in active tectonic drilling, but also for geomechanical and well bore stability analyses. Certain in situ tools were not previously available for scientific ocean drilling due to the borehole diameter and open hole limits of riserless drilling. The riser-capable drillship, D/V Chikyu,now in service for IODP expeditions, allows all of the techniques available to estimate the magnitudes and orientations of 3-D stresses to be used. These techniques include downhole density logging for vertical stress, breakout and caliper log analyses for maximum horizontal stress, core-based anelastic strain recovery (ASR, used in the NanTroSEIZE expeditions in 2007–2008), and leak-off test (Lin et al., 2008) and minifrac/hydraulic fracturing (NanTroSEIZE Expedition319 in 2009). In this report, the whole operational planning process related to in situ measurements is reviewed, and lessons learned from Expedition 319 are summarized for efficient planning and testing in the future

Surveillance in deep water wells is cost prohibitive. There is a need for significant hydrocarbon production or water shutoff incentive to justify the intervention in such wells. The wells straddle multiple stacks of soft sediment reservoirs, being completed with open hole gravel pack. While laterally extensive barriers between various sands units might help the water shutoff / containment, the gravel pack annulus still provides a conduit for water to move upwards and jeopardize the shutoff success. In this campaign a meltable alloy was deployed to plug the flow in both annulus and screens. In deep water subsea wells, water conformance control is often attempted blindly without flow diagnostic surveillance or production logs as a minimum. This can impact the production due to plugging substantial hydrocarbon production or inadequate flow from the remaining zones. Candidate wells or techniques for shut-off require robust diagnostics to improve the success rate and limit loss of oil or gas production. In a recent well work campaign production logs were acquired to optimize the water shut-off. Well access is challenged by limited rigup height (short lubricator) and well deviation. The well trajectory impacts the phase presence, mixing and recirculation. It requires a short array of sensors conveyed on tractor. Logging while tractoring capabilities in surface readout mode is required to minimize the rig time, improve depth control and perform real time data quality assurance. The multiple mini-spinners, electrical and optical probes are all positioned to the well's vertical axis to capture all local changes in the flow regimes. Sensor arrangement is sufficiently compact in this tool to minimize flow disturbance by tool occupancy and movement along the well. Real-time profiling of the complex flow regimes during the acquisition provided better log control and understanding of the downhole phase dynamics. Changing the mindset about subsea deep-water reservoir surveillance paid dividends in water shutoff operations, both for immediate decision make and for longer term well and reservoir performance management. There was a net benefit by deploying a compact axial array production logging string that allowed accurate rate and phase allocation and further identification of zones to be isolated using an innovative plug-back method that significantly reduced the water production.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractChina National Offshore Oil Corporation (CNOOC), Chevron, and ENI, the field operator, are partners in the development of the HZ oil and gas fields, operating as the CACT Operators Group (CACT) in the South China Sea. The HZ fields are stacked, thin, high-permeability sandstone reservoirs interlayered with low-permeability layers. The shallower layers generally have better permeability and were developed first while the deeper, lower-permeability reservoirs have been developed more recently.The lower-permeability reservoirs are generally of lower porosity and higher compressive strength. Drilling-mudfiltrate invasion also tends to be deeper. Deep-penetration perforating charges are required to perforate past the damaged zone. Experience indicates that underbalance perforation provides better productivity compared to overbalance perforation.Although conventional underbalance perforation can be performed using pipe-conveyed or tubing-conveyed perforation (TCP), depth uncertainties and the time requirement for TCP service in thin reservoir zones makes wireline-conveyed perforation an attractive method. However, where multiple zones must be perforated, the conventional wireline approach can only perforate the first zone underbalance (with the completion fluid weighted accordingly) while subsequent zones could only be perforated balanced at best. A new perforating system, designed to generate a large dynamic underbalance with a static overbalance, was used to perforate new wells for the development project to maximize well productivity per well expenditure.A multilayer production evaluation of one of the wells perforated with the dynamic underbalance method produced a zero skin value in the 9-md layer and a -0.97 skin value in the 1600-md layer. Conventional underbalanced perforation, employing multiple wireline runs, could not achieve these low skin values over this wide range of permeabilities. and z w = 15.4 ft in TVD, θ= 32 deg) 1.672 +/− 0.5 Completion Skin Factor Sensitivity Analysis Completion Skin Factor = 2 J ss , PI (STB/D/psi) 12.449 2.600 (stdev) J pss , PI (STB/D/psi) 13.254 2.780 (stdev) Completion Skin Factor = 1 J ss , PI (STB/D/psi) 13.546 2.931 (stdev) J pss , PI (STB/D/psi) 14.504 3.153 (stdev) Completion Skin Factor = 0 J ss , PI (STB/D/psi) 14.854 3.261 (stdev) J pss , PI (STB/D/psi) 16.015 3.537 (stdev) Completion Skin Factor = −1 J ss , PI (STB/D/psi) 16.443 3.607 (stdev) J pss , PI (STB/D/psi) 17.876 3.953 (stdev) Completion Skin Factor = −2 J ss , PI (STB/D/psi) 18.412 3.934 (stdev) J pss , PI (STB/D/psi) 20.228 4.377 (stdev)

Drill stem test (DST) derived average effective permeability and productivity is our industry's accepted standard but DST expenses are not always justified especially in development wells. Although zonal contribution could be measured by production logging survey but this requires an additional well intervention operation and most likely interruption of production as well. Zonal productivity modeled correctly in a well is of immense value for reservoir management. In exploration well, accurate productivity index prior to DST is invaluable for operational planning, while in development well accurate productivity index is crucial for completion design.If dynamic data is not available, zonal productivity had been estimated based on permeability derived from petrophysical log data. Single probe open-hole wireline formation tester (OH-WFT) pretest mobility is often used to calibrate log data estimated permeability. However, OH-WFT pretest almost always measure the invaded or drilling induced damaged zone and is at a scale much smaller than DST derived average permeability. DST 1699.36 -1699.5 m WFT 1707.5 m Pretest and Sampling DST 1699.36 -1699.5 m DST 1699.36 -1699.5 m WFT 1707.5 m Pretest and Sampling