Safe and efficient drilling process

Programme 1 addresses technologies to avoid drilling related problems and to improve safety and drilling performance. 
  • Drilling problems are related to surface drilling equipment, drillstring, drilling fluid and formation integrity, and control of these elements
  • Improvement in drilling performance requires new solutions with respect to equipment, methods and control

Reliable and accurate information will always be critical. It opens for significant improvements in early detection of unwanted events, optimisation and automation of drilling processes.

Programme manager: Jan Einar Gravdal
Deputy: Harald Linga

Project summaries follows. Please see the annual reports for details.

Project 1: ROP Management (2011-15)
Phase 1 was completed end 2014, reporting results on cuttings transport modelling, hook-load measurement corrections, drill-string mechanics and drill-string vibrations.

Project 1, Phase 2: Drilling Process Optimisation (2015-19)

Drilling is a rather complicated process to manage where:
  • The drilling efficiency is constrained by many, possibly, conflicting factors (e.g. need for a high drill-string rotational speed to drill faster and facilitate the transport of cuttings but at the same time avoid drill-string vibrations),
  • Much time may be used in activities that do not make direct progress (so-called flat time operations like running casing, tripping, etc.),
  • Numerous incidents (e.g., pack-off, stuck-pipe, kick) may cause delays (NPT – Non Productive Time) or jeopardise the safety of people, the installation and the environment.
  • There are substantial uncertainties about the drilling and geological contexts, both prior to drilling the well and during the well construction.
The research question addressed by the project is whether there is a way to optimize the overall performance of a drilling operation while managing drilling risk and accounting for uncertainties?

The main objective of this project is to assist a drilling team in optimizing the overall performance of drilling operations from the planning stage to the execution phase while managing drilling risks with respect to the currently foreseeable geological and drilling uncertainties.

Project Methodology
The project management methodology is the following:
  • The project has four concurrent timelines:
    • To develop prototype tools to assist the drilling process management,
    • To conduct studies in order to constantly verify the applicability of the developed methodologies,
    • To analyse and prepare the necessary conditions to introduce the new methodologies developed in the above mentioned prototypes inside the industrial partners’ organisation and work procedures, also referred as the “socialisation” of the new technologies,
    • To support student education.
  • Each timeline has a series of deliverable results,
    • A milestone plan paves the way to each deliverable result,
    • At each milestone, the project team reports to the industrial partners if the milestone is reached and which adjustments are necessary to reach the deliverable result,
    • Testing periods, at each of the industrial partners, are included into the milestone plan in order to guide the development.

Deliverables 2016-2019

Prototype 1 (DrillOpPlan):
DrillOpPlan is a working prototype of a drilling engineering tool that optimize, before a drilling operation, the sequence of drilling parameters (ROP, RPM, Flow-rate) to be used during a drilling operation in order to minimize time, yet avoiding potential drilling incidents. The system makes use of past information from previous drilling operations. It evaluates the uncertainty of the predictions in order to quantify the associated risk.

Toward the end of the development of this prototype, it will be investigated which software company is best suited to industrialise and commercialise the resulting application.

Prototype 2 (RT-Hub):
RT-Hub is a data acquisition system that can connect to multiple data sources and can apply advanced correction methods on measurements. The data acquisition system also calculates the accuracy on the provided values. The prototype is demonstrated at Ullrigg and is ready for industrialization.

We will investigate whether this can be integrated in the applications portfolio of existing companies delivering data acquisition servers.

Prototype 3 (RT-DrillOpt):
RT-DrillOpt is a real-time advisor system that can be hooked up into a drilling control system. It provides acceptable range of ROP, RPM, WOB, flow-rate to maintain a fast but safe operation. The permissible values are displayed directly on the drilling workstation screens. The prototype is demonstrated using Cyberbase from NOV and/or DrillView from MHWirth using the Virtual Arena facilities.

Project manager: Eric Cayeux
Deputy: Knut S. Bjørkevoll

Project 2: Formation integrity (2011-14)

Extended leak-off test (XLOT) is one of the few techniques available for stress measurements in oil and gas wells. Interpretation of the test is often difficult since the results depend on a multitude of factors, including the presence of natural or drilling-induced fractures in the near-well area.

Project description and results
In this project, coupled numerical modelling of XLOT has been performed in order to investigate the pressure behaviour during the flow-back stage as well as the effect of a pre-existing fracture on the test results in a low-permeability formation. Essential features of XLOT known from field measurements have been captured by the model, including the saw-tooth shape of the pressure vs injected volume curve, and the inflection in the pressure vs time curve during flowback used by operators as an indicator of the bottom hole pressure reaching the minimum in-situ stress.

Project manager: Andreas Bauer
Deputy: Hans Joakim Skadsem

Project 3: Managed Pressure Drilling (2012-14)

For drilling narrow pressure margin wells or in depleted reservoirs, Managed Pressure Drilling (MPD) is seen as a valuable method. However, the level of instrumentation and in particular access to downhole pressure data is a limiting factor to achieve accurate and robust pressure control. One key research topic has therefore been to investigate these limitations and also the possibilities when increasing the level of instrumentation, e.g. by wired drill pipe, or by using well flow models. 

Project description and results
Possibilities and limitations by using back-pressure MPD has been an ongoing topic since 2013. Experiments using a high fidelity well flow model have resulted in several papers listed below. A new topic in 2014 has been alternative well control procedures, specially adapted to back-pressure MPD equipment and instrumentation level. A kick incident during MPD operations is typically handled by conventional well control methods, at least if the kick is estimated to be larger than a threshold value. In this project two alternative well control procedures specially adapted to backpressure MPD have been evaluated: the dynamic shut-in (DSI) procedure and the automatic kick control (AKC) procedure. Both methods capitalize on improvements in Pressure While Drilling (PWD) technology. A commercially available PWD tool buffers high-resolution pressure measurements which can be used in an automated well control procedure. By using backpressure MPD, the choke valve opening is tuned automatically using a feedback-feedforward control method.

The two procedures are evaluated using a high fidelity well flow model and cases from a North Sea drilling operation are simulated.  

Project manager: Jan Einar Gravdal
Deputy: Knut S. Bjørkevoll
Project 4: Determining Changes in OBM during Well Control Situations (2013-16)
It is important to understand the behaviour of kick–oil-based mud (OBM) interaction along the well in order to plan for safe drilling operations. Slow leaking methane and gas diffusing from a reservoir will be absorbed even in overbalance situations. The ability to understand and to simulate such effects will improve the understanding of the behaviour of the well when using OBM.

Drilling simulators are tools for analysing kick detection limits, designing well control procedures, planning the chemicals and equipment needed on the rig, and generally planning the well design. Due to the complexity of the chemistry and physics in kick–OBM situations, a good dynamic simulator is needed, since difficult and dangerous situations often happen as the kick is circulated out. Good dynamic simulators with OBM capability are hard to come by, and since they are being based on ideal equations, there is a need for verification through experiments.

Project objectives and expected results
The project has the following main objectives:
  • Produce accurate values of density and viscosity for different degrees of CH4 saturation for a specific OBM at pressures (P) and temperatures (T) appropriate for drilling operations
  • Produce accurate measurements of solubility of CH4 in OBM
  • Study the dynamic absorption of CH4 in a kick situation
  • Find out if 'paraffin' base-oils behave similarly to 'normal' base-oils
  • Compare results with theoretical models
  • Use results to build computer subroutines for use in dynamic simulations (well control simulations, training simulator)

Expected results of the project will be:
  • Tables of measurements in P and T space and various levels of saturation
  • Properties comparison of the OBMs with 'paraffin' and 'normal' BO
  • Interpolations from measurements made by use of reliable software (PVTsim)
  • Density and viscosity tables of OBM mixed with reservoir gas in P and T space as input to well flow model

Anticipated application of results will be as follows:
  • Dynamically predicting OBM behaviour in a real well (improving drilling safety)
  • Dynamical simulations of flow during kick situations
  • Input for dynamic two-phase gas-liquid flow model
  • Results will make possible more accurate modelling of two-phase gas-OBM flow in the well
This project will help build experience and expertise by combining measurements and theory. This may result in producing a minimum set of needed measurements in the future, which will make obtaining reliable models for other OBMs quicker and more economical.
Project manager: Harald Linga
Deputy: Jan Einar Gravdal
Project 5: Well Control Simulator (2016-19)

Motivation is twofold:
  • The calculation of gas-fluid interaction involved when taking and handling inflow of reservoir fluids into drilling fluids is of key concern for accurate gas kick predictions. Current well control models are outdated – with little development in basic modelling over the last couple of decades. Furthermore, data on gas mass transfer with drilling fluid is limited, for example when predicting the dynamics of gas dissolved in oil when taking a kick, and of gas boiling out when moving upwards in the annulus.
  • Use of data driven model calculations to support real time decision support and automation puts very high requirements to calculation speed, robustness, stability, and user-friendliness. Further efforts are needed to obtain these requirements while at the same time representing the physical process with high accuracy. 
Static periods, including flow checks and longer unplanned stops, will be used as a central example to obtain more accurate interpretation of observations and better prediction of consequences, although much of the work will have more general value. More accurate calculation of taking a kick, stopping operation and then stay static for a given time, will give a more accurate picture of the correspondence between fluids involved, reservoir properties, and the response seen by sensors. The calculations will also address damages and risks associated with flow checks and static periods.

Work done in P1.6 shows significant deviation between experimental data and current models, and, the project will exploit the HPHT-data taken there to improve the calculation of how gas influences PVT and rheology characteristics and its impact on time dependent effects of gas going into solution and dissolving.

Quantifications of the effect of uncertainties in modelling and input data will be addressed in cooperation with P1.3 because these are often large and should be taken into account when making decisions.

Operationalization and use of results will be discussed with participants and considered from the beginning of the projects because applications to well control operations is likely to depend heavily on how deliveries are fit to operational needs and limitations. This work will also be in cooperation with P1.3.

The project objective is to develop improved calculation algorithms for mixing and flow of drilling fluids and reservoir fluids, with special focus on prediction of effects that influence how kicks are taken and mixes with drilling fluid during static periods. The calculations will be implemented in a prototype tool that can be used for improved planning. The implementation will aim at combining accuracy with simplicity and robustness to make methods fit for later use in real time applications like automated decision support and control. The goal is to improve interpretation of observations and reduce risk of unwanted side effects.

Quantify effect of model and data uncertainties in cooperation with P1.3.

Take into consideration operationalization with input from specialists and DrillWell participants when developing detailed plans and deliveries. Although operationalization and commercialization mostly will follow after this project, the question of whether the research work planned will suit the more practical needs following after the project will be brought up for discussion.

Project manager: Knut Steinar Bjørkevoll
Deputy: Jan Einar Gravdal
Project 6: Reduced uncertainty in overpressures and drilling window prediction ahead of the bit (PressureAhead) (2016-18)

Knowledge needs
Oil and gas exploration and production wells have been drilled on the Norwegian Continental Shelf for the last 45 years, both in overpressured areas and in hydrostatic pressured areas. Still, with long expertise, drilling teams experience large uncertainties in prediction of pore pressure and well stability, and this may lead to non-productive time due to unexpected events such as stuck pipe, mud losses and well control events. Water fluid pore pressure variations are still not fully understood, neither in exploration areas nor in mature areas. Better constraints on the overpressures prognosis ahead of the bit could have large impacts on drilling campaigns.

At present, different methods are used to calculate the overpressure and mud window (interval in safe well mud pressure, ranging from borehole collapse to hydraulic fracturing), with no unified use of input parameter. Only occasionally an uncertainty evaluation in the pressure and stress prognosis is carried out prior to drilling campaigns. The new methods proposed in this project and tighter integration between software tools will result in reduced number of well control events by making more accurate predictions with real time update available to the drilling team. Avoidance of pressure related accidents will save typically one or several days of delay in drilling program and thus on average 5 MNOK or more. In the best case, possible side step drilling can be avoided by using the new and improved technology.

The objective is to simulate and predict pressure and mud window ahead of the bit, with special attention to analysis of uncertainties. The uncertainty for both pressure and mud weight window will be automatically narrowed as new updates of pore pressure while drilling is included. One objective is to simulate the effects of stresses on pressures, and possible reactivation of faults. A secondary aim is to obtain:
  • Better constraint on uncertainties in the modelling set up,
  • more robust coding algorithm,
  • automated uncertainty calculations are parts of the methodologies to be included,
  • better constraint on the uncertainty in the real-time update data.
The expected outcome of the project will be a software where the same input parameters are
used for both pore pressure prediction and well stability prediction with uncertainties. The
new tool should reduce significantly the gap between sophisticated mathematical models and
operational needs of the drilling team.

Project manager: Ane Lothe
Deputy: Jan Einar Gravdal


Jan Einar Gravdal

Harald Linga

Eric Cayeux

Knut S. Bjørkevoll

Andreas Bauer

Hans Joakim Skadsem

Ane Lothe