The technically challenging development of the marginal resources in the mature fields in the North Sea requires new levels of planning and execution to control the drilling process.Over the past few years, improved dataflow between drilling rigs and shore-based operator and service providers support organizations has created a renewed interest in automated monitoring of drilling parameters. Development of data transmission systems like InterACT and data formats like WITSML have initiated the search for and the development of new sensors that can be used for automated real-time monitoring of critical drilling fluid parameters.Increased focus on HSE in general and the use of harmful test chemicals, vapors and the risk of explosions in particular also has been an important driver for this development. Introducing a level of automation described in this paper can reduce by 70-80% the exposure time of fluids engineer in the rig laboratory without compromising service quality.Moreover, the development and use of advanced hydraulic simulation programs frequently employed for extended reach drilling and managed pressure drilling (MPD) have increased the focus on more reliable and more frequent operational inputs. The precision of modern simulation software represents a sharp contrast to the current practice of manual rig testing and reporting.This paper details the selection of fluid parameters considered most important for automation. The authors will describe the sensors developed for monitoring the most important parameters, including Electrical Stability (ES), density, temperature, water content in invert emulsion drilling fluid, XRF elemental analysis, in-line particle size distribution (PSD) and full 3D rheology tests. The parameters that could be monitored with existing sensor technologies used in other industries will be discussed, as well as those requiring development based on current field equipment. In addition, the paper will describe the installation and first field experiences with a full range of automated instruments on various rigs in the North Sea. Software System and InterpretationOne of the primary reasons more operators and oilfield service companies have renewed their interest in real-time monitoring of fluids data is the ensuing development of new data transmission possibilities, including widely available high-capacity broadband internet access to drilling rigs. Early in the automated fluids measurement project, WITSML was chosen as the preferred infrastructure for sending and receiving data between the rig and operations centers for the operator and the service providers. Today, WITSML servers are available worldwide with proven ability to send and receive large data volumes at a reasonably high speed for distribution to all knowledge hubs involved in the operation.All of the instruments purposely designed and built for this development project were equipped with individual IP addresses and the ability to communicate directly through WITSML servers, as Fig. 12 illustrates. Operational communica...

Health and safety concerns and technically challenging wells in the North Sea have created a clear and present requirement for robust systems for automated, real-time measurement of key drilling fluid parameters. This paper discusses a suite of discrete sensor packages that has been developed, successfully yard-tested, and deployed in different configurations on three critical wells in the Norwegian sector. They replace manual measurements that have been in use of over 60 years. Specific parameters addressed by this suite include density, temperature, electrical stability and water content in oil-based fluids, elemental analyses, solid content, particle-size distribution, and multi-temperature rheological properties.Industry has long recognized the value of automated drilling fluid measurements for reducing personnel on board and isolating remaining personnel from potentially hazardous areas, mitigating non-productive time, rapidly diagnosing problems, providing necessary input to various drilling automation processes, optimizing fluid performance, and sharing real-time data with remote operating centers. Successful implementation had been plagued by the lack of suitable sensors and efficient means to transfer and interpret the data. Business issues also had been of concern, but fortunately most of these are steadily being defused.This paper describes each of the sensor packages, including the design, method of operation, accuracy, reliability, interpretation, and means of data transmission. Two sensors in the suite that have been previously available are included for completeness. The authors present sample yard and/or field data, demonstrating typical results as well as suggesting how these results could be leveraged for maximum benefit.

This paper describes the successful use of Focused Beam Reflectance Measurement (FBRM) for remote real-time monitoring and management of drilling fluid Particle Size Distribution (PSD) while drilling in a depleted HTHP gas reservoir in the Norwegian sector of the North Sea. Drilling into depleted reservoirs is challenging as the fracture strength of the reservoir is reduced due to pressure depletion from production. Experience has shown that adding suitably-sized blends of calcium carbonate and synthetic graphite to the drilling fluid can significantly improve the fracture strength. Optimum particle blends and size distributions are designed based on expected fracture and formation pore size. In order to maintain the formation strengthening effect, the PSD of the designed blend must be maintained during drilling and circulation of fluid. Furthermore, the method employed must be able to capture the changes in size distribution from the accumulation of drill solids and the mechanical attrition of particles in circulation. Monitoring and managing PSD effectively while drilling has been hindered by lack of suitable equipment for real-time measurement. The successful application of the FBRM technique has shown that reliable data can be obtained and that these data compare well with other conventional PSD measurement techniques. This paper describes how the online PSD measurements were utilized to improve engineering of the drilling fluid to obtain full effect of the formation strength enhancement provided by the added particulate material. The improved PSD control can be used both to ensure sufficient concentration of correctly sized particles to effectively bridge the pore throats in the sandstone formation and at the same time include an ideal concentration of larger sized particles to plug fractures. Good solids control management allowed efficient screening of particles and when combined with addition of new material, provided full control of the total particle concentration. Introduction As oil-producing fields in the North Sea are gradually becoming more mature, requests for more advanced drilling techniques and equipment to mitigate problems associated with the depleted reservoirs are becoming more commonplace. For example, the current development campaign for the mature parts of the Tampen area in the Norwegian Sea, such as the Kvitebjørn field, is planned drilled using Managed Pressure Drilling (MPD) techniques to reduce overbalance while drilling. Planning of the operation also includes a raised focus on preventative treatments for induced and natural fractures. The control of particle size distribution (PSD) while drilling has become an important issue with respect to particle additions, maintenance and solids control management (Omland et al. 2007). Regular monitoring of the drilling fluid PSD is most convenient if it can be handled on site, which requires a granulometer to monitor at least the trend in the PSD. Electrical or optical methods like laser light scattering can be used; an even simpler technique is wet sieve analysis, which has the advantage that fine drill solids and weighting material can be removed so that the measurements reflect the PSD of the added wellbore strengthening or formation bridging material. Common to all these methods are that they require sampling of the drilling fluid with the inherent problems this entails with sampling accuracy and sample preparation. There is a growing demand within the oil industry to identify equipment that can perform real time measurement of PSD directly in the drilling fluid thus providing the potential for improved monitoring and control of particle additions.

To successfully perform a Managed Pressure Drilling (MPD) operation in a high-temperature, high-pressure (HTHP) field offshore Norway, an innovative fluid technology was developed for well control purposes. The drilling fluid used in MPD mode had insufficient density for tripping operations. To balance the reservoir pressure when tripping, an isolation pill was spotted in the upper part, leaving dense fluid on top of the well and making the total hydrostatic pressure in the fluid column sufficient for well control. This development pill enabled pressure to be transmitted to the bottom of a well by placing the pill in between a dense fluid on top of a less dense fluid. The design and properties of this pill made it possible to run test wireline logs and eventually a test liner run through the pill, and at the same time, maintain a pre-determined hydrostatic pressure to keep the well under control without externally applied pressure. In addition, the pill did not cause instability by interfacing different density fluids as this would have a dramatic impact on the hydrostatic pressure. One of the criteria was to displace the pill out of the well by using the circulating system only. As this paper describes, the pill stayed intact during the entire operation and displacement of the pill from the wellbore was performed successfully. Another benefit observed was the lack of remedial treatment needed at surface when the pill was circulated out. As this was a solids-free pill, no additional treatment was required. This paper describes in detail the development of the fluid pressure transmission pill and the purpose of using such a pill, including testing performed, and the final result of using the pill for the first time in a well exposed to open reservoir. Introduction A Fluid Pressure Transmission Pill (FPTP), also known as a "Balanced Mud Pill", was developed for use in logging and completion operations during Managed Pressure Drilling (MPD) operations in the Kvitebjørn field. MPD operations have gained popularity for development of modern HTHP gas fields. Batch drilling of entire fields is a high risk and big cost approach. However, due to the rapid pressure drop common in many gas reservoirs after the initiation of production, the pressure regimes for drilling the remaining wells in the project are more challenging. The specific background for the development was well 34/11-A-13 T2 in the Kvitebjørn field. Density for the tests was chosen at 1.87 SG, which was the predicted fluid density while drilling in MPD mode. Required equivalent mud weight to balance the reservoir pressure was estimated to be 1.91 SG and the plan was to use 2.08-SG Cs-Formate mud above the FPTP to achieve this density. The primary target for the project was to develop a crosslinked polymer pill with sufficient integrity to isolate the highdensity brine or drilling fluid in the upper section of the well from the lighter fluid in the deeper section. This would save the cost and logistic challenges of having to displace the entire circulating system to balance the reservoir pressure. The FPTP should also serve as a contingency plan if it should become necessary to open the choke to pull out of the hole without having to displace the entire well volume; thus the pill should be able to transmit the hydrostatic pressure of the added high-density fluid above to the open hole below. The pill should provide sufficient flexibility to enable tripping, allow logs to be run, and finally enable running of liners/production screen assemblies and yet not allow the high-density fluid to channel through it.

Specifically selected and manufactured organic fibres were used to bridge microfractures and stabilize shale and mudstone formations while drilling the Fiqa, Shilaif, Mishrif, Maddud and Nahr Umr formations and during a 5-day logging interval at the Mishrif formation. A newly developed method for testing invasion depth in 20/40 gravel pack sand, in order to monitor the fluids' bridging capability, was developed for drilling and logging the unstable Middle Cretaceous formations. The information from the tests was actively used to monitor and maintain the concentration of organic fibre materials in the drilling fluid to reduce invasion and to stabilise the highly fractured and layered shale and mudstone. A treatment programme was established around the data collected, using drilling fluids from the active system with a high concentration of fibres which was streamed back into the active system accordingly. The depletion rate was recorded and compared with the various formations during drilling. The drilling fluid chosen for the project was a water-based system, with 14% NaCl to balance the activity (AW) and formulated with a polyamine clay inhibitor. The section was planned with an extensive logging program in the Mishrif formation. Drilling had to be slow and controlled for parts of the Nahr Umr formation to pick the casing setting point in top Shuaiba formation. The hard and brittle shales found in this group of formations have been problematic for drilling in the Arabian Peninsula for a long time. The Nahr Umr formation is particularly known for its loose structure and frequent hole collapses which are caused by fluid penetration along pre-existing fractures and laminated surfaces. Oil-based drilling fluids are the preferred systems of choice to reduce the capillary effect of invading fluids, and the consensus is to reduce the exposure time for the formations as much as possible. As a water-based drilling fluid was chosen, a program was set up to focus primarily on a rapid build-up of a filter cake to bridge fractures and reduce filtrate invasion. The chosen organic fibres are anionic in nature and therefore have an affinity to the broken edges of clay platelets with a proven ability to create a network with particles that bridge the formation. The 12 ¼" section was drilled without stability issues and without remedial back reaming to the logging depth. The top part of the 12 ¼" section was kept open for 5 days during logging. The Nahr Umr formation was drilled with a controlled, low ROP to identify the setting depth for the 9 5/8" casing in top Shuaiba formation. Total open hole time was 4 days after logging. The casing was cemented without losses or other operational issues. The use of specific organic fibres to stabilise highly fractured shale formations presents a low cost and efficient method for dealing with a high-cost problem associated with significant NPT. Real time data collection and close monitoring of the fluids bridging capability using a fluid-invasion test kit proved to be an effective method for responding quickly to changes in hole stability, formation strength/integrity and fluid invasion. A quick mix and bleed method of additions based on the data collected is presented as a key finding. The novel treatment programme is shown to give practicing engineers a system and toolkit that works when dealing with the known problems associated with the Nahr Umr shale formation.