For HPHT wells it appears that the only industry practice for open hole sand control has been Stand Alone Screens (SAS), even for wells that should have been gravel packed. For North Sea HPHT field developments, SAS has been chosen as the open hole sand control method. However, according to company best practice, these wells should have been gravel packed. General skepticism around gravel packing for these wells is primarily based on the risk of losses. A study was initiated to look closely at potential losses during gravel pack pumping when compared to SAS in HPHT environment. Key issues:a. Narrow margin between pore pressure and fracturing gradient b. Well control risks, technical risks and cost c. Fluid selection The basis for the study was to perform gravel packing with conditions as close as possible to the planned low well angle SAS wells solution. The screens were to be run in screened reservoir drilling fluid. This fluid contains filtercake repair particles. It became natural to evaluate this fluid also as a carrier fluid for the gravel, thus mitigating the risk of losses. Due to small margin between pore pressure and fracture gradient, the gravel pumping operation would have to be planned to be performed at low rates. To qualify the HPHT gravel placement, yard testing was performed in a mini-scale gravel pack model. Gravel was placed successfully at low rates with screened reservoir drilling fluid. Very little degree of settling in horizontal surface lines was observed at low pump rates, hence no practical consequences is expected for this in high angle well sections. Furthermore, flowback testing in lab was performed on the particle containing carrier fluid. The major findings in this study were: --Gravel can be placed effectively at low rates, minimizing ECD impact in a narrow pore/frac operational window.--Gravel can be placed using screened formate based Reservoir Drilling Fluid (RDF) maintaining the filtercake intact and with minimum risk of losses. --The particle containing carrier fluid has no adverse effect on gravel pack permeability.

Based on the experimental evidence and th_se simulations, it is probable that the glass displacement events in ISV melts are caused by sudden gas releases. ® Adjacent melts or other media that block vapor transport on three sides of the melt slightly increase (~0.5 psig) the gas pressure beneath the melt. The temperature aJ_dsaturation distributions in the soil are drarnatically affected by such structures. ® Melt growth down the electrodes is likely to be the normal mode of melt progression for fixed electrode tests, This can probably be avoided by dynamically feeding the electrodes downward as the melt advances. • Phase resistance between electrodes in a melt can be accurately predicted by TEMPEST and a simple equation presented in this paper, Melt diameter can be predicted given phase resistance and centerline depth, However, melt growth down fixed electrodes _ be distinguished from an oblate spheroid melt shape using melt centerline depth and phase resistance information.

The newly developed high-temperature high-pressure (HPHT) exploration oil-based reservoir drill-in fluid (RDF) was specifically designed with formation damage, pressure logging and geochemical analysis in mind. Requirements for a reservoir drill-in fluid that performs well under HPHT conditions, has good pressure log response and is geochemically distinguishable from reservoir fluids were the driving forces for the development of this system. The high-performance, low-damaging system combines several new products. Laboratory results have shown good rheology profiles, tight HPHT fluid loss control, high return permeability values and excellent long-term fluid stability. The system was developed to replace today's standard paraffin systems which occasionally struggle with irregular and too high viscosities with poor fluid stability over time. This occasionally leads to various drilling issues and barite sag problems during low shear or static conditions. Laboratory testing has documented the qualities of the new system, followed by a very successful field trial, where low impact on geochemical tests was obtained. This paper details the development of the fluid, the testing performed to qualify it for the field trial and the successful results from that field trial. Furthermore, the paper also details the high return permeability values and the mechanisms within the system that allow these goals to be achieved. The fluid has properties that make it an extremely strong candidate for reservoir drilling in general.

Open hole gravel packing of reservoir sections drilled with oil based fluid is traditionally performed with an aqueous carrier fluid. This typically involves displacing oil based fluid to aqueous fluid once the gravel pack screen is in place. In reservoirs with swelling or unstable shale this approach reduces the risk associated with open hole exposure to aqueous fluid over time. However experience has shown that instability can still occur resulting in an incomplete, or even an aborted gravel pack. In addition, mixing of incompatible oil and water based fluids downhole has the potential to generate very viscous emulsions that negatively impact gravel pack efficiency and well productivity. The objective of the new technology was to maintain borehole stability, eliminate fluid incompatibility and enable a complete gravel pack.An oil based carrier fluid has been developed and qualified using laboratory and yard scale testing. The fluid is a solids free invert emulsion that exhibits near Newtonian rheological behavior; thereby promoting settling of proppant during gravel packing. The density of the fluid is controlled by adjusting the volume fraction and density of the brine phase. The fluid has been qualified up to a density of 1.25 SG with further potential to achieve a density of 1.63 SG.The oil based carrier fluid has been introduced on a mature field, with a long history of gravel pack completions. Progressive reservoir depletion has created operational challenges, resulting in inconsistent gravel pack performance. Consequently, several procedural changes have been implemented over time. Reservoir inclination is typically up to 50°, open hole length up to 200 meters, and bottom hole static temperature around 90°C. Gravel packs were most recently performed with a 1.10 SG aqueous carrier fluid.The new carrier fluid has exhibited stable properties during implementation on multiple well completions. Gravel pack efficiencies have been consistently good, at 100% or higher. As a result, well productivity expectations have consistently been achieved or exceeded. The operational time for installing the lower completion compares well with the traditional approach with aqueous fluid.The implementation of oil based gravel packs in multiple wells, allows a comparison with brine based gravel packs in the same field. It is therefore considered to be an industry first.