The traditional plug-and-abandonment (P&A) method of exploration wells in the North Sea is to set a series of cement plugs to isolate the pressurized zones from each other and from surface. This paper describes a North Sea P&A field case. In this case, an alternative method was used with a Bingham-plastic unconsolidated plugging material with high solids concentrations. This alternative method addresses well-integrity issues such as those caused by shrinking of cement or gas migration during setting, fracturing after setting, or long-term degradation by exposure to heat and chemical substances in the well.The gas-tight well-barrier element described here does not set up after placement and does not shrink. Furthermore, it cannot fracture even when shear forces exceed its strength. When this happens, the material floats and shear forces are reduced below yield strength, causing the plug to reshape. Because this is a purely mechanical process, the transition between solid and fluid phase is repeatedly reversible (in principle, an infinite number of times).The plug is thermodynamically stable because its sealing property is decided by the solids particle-size distribution (PSD) and bound water only. The closely packed particles and absence of free water mean that the entire column is kept homogeneous and no internal redistribution of particles may occur. Hence, the permanent gas-tight barrier will prevent influx through the wellbore.In the field case, a successful implementation of the technology was obtained. The field case shows how the fast and efficient placement of the plug contributes to overall cost reduction. The paper explains how the well-barrier element complies with Norwegian requirements for permanent P&A; these requirements also apply to the UK sector (NORSOK D-010 2004;Oil and Gas UK 2009). Operational procedures are also presented in some detail.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSubsea re-injection of drilled cuttings has been applied on the Åsgard field to handle oil wet cuttings. For various reasons, oil based drilling fluids have been used in all 12 ¼" and 8 ½" sections at Åsgard. Discharge of oil wet cuttings is not permitted. Cuttings have to be re-injected to the formation or sent onshore for treatment. Onshore treatment and logistics, are expensive and involve a large emission of CO2. If reinjection can be performed, big bag handling operations are significantly reduced. Furthermore, it is difficult to have reliable logistics to bring cuttings onshore. Therefore, cuttings re-injection is the optimum solution for this operation, where the preferred injection point is below the 20" casing shoe.Re-injection is straightforward if cuttings can be reinjected into a formation underneath a large sand formation where the liquid phase of the slurry can leak off. At Åsgard there are no such large sands. Therefore, cuttings have to be re-injected into shale formations. Since the fluid does not leak off sufficiently fast in shale there is a danger that the annulus may be exposed to a too high pressure for a long time. If too large a fluid volume is injected at a time, there is a danger that the fluid may propagate as a fluid bubble to the surface.Leakage to surface has been observed four times at Åsgard. It has been recognized that the cementing results must be better than normal to hinder leakage to surface if cuttings are re-injected into shale formations without sand layers. This paper describes the leakages in detail. It focuses on the necessary improved drilling and cementing precautions to hinder leakage. The paper also describes a technique with alternating re-injection and static periods to make the liquid phase leak off into minor sands and shale, preventing the formation of too high an annulus pressure and hindering the formation of a fluid bubble propagating to the surface.

The South Umm Gudair (SUG) oil field located in the Neutral zone between Kuwait and Saudi Arabia has produced since 1968 from an active water drive carbonate reservoir of Lower Cretaceous age. The lower zones are homogenous intervals of higher permeability which appear to be sufficiently swept by natural water drive over a period of time. The upper zones of the reservoir have lower permeability, are relatively thin and are bound by tighter intervals that act as possible barriers to the natural water drive system.Geosteering techniques are now extensively used in oil and gas industry for horizontal wells to produce hydrocarbons from thin reservoirs to maximise recovery, and restricting water-coning problems. Recent advancements in well placement using Geosteering allow successful targetting of low permeability reservoir with great precision which results in exposing more drainage area in the target pay.The geosteering technique was considered for the first time in joint operation’s SUG field targetting two horizontal wells. Improved well productivity is achieved through optimised well placement. This success has led to a development plan and strategy of additional horizontal drilling locations to maximise recovery of un-swept oil from the low permeability reservoirs. This paper reviews the success of Geosteering in SUG’s two horizontal wells, completed in July 2004.