Annex 1 - Drilling and completion work programme
Annex 1 to The Danish Working Environment Authority (WEA) guideline 65.2.2 on Health and safety aspects regarding offshore well operations
Information about the well and drilling
To the extent possible, the international system of units (SI) should be adhered to, and the drilling programme shall as a minimum contain information about the following:
- the ID number of the well as given in the Danish Energy Agency numbering system
- the name of the well. Wells not named by the operator will be named by the Danish Energy Agency
- name of operator and information about the operator's organisation in connection with the drilling operation and the rig owner’s organisation and other companies involved
- well surface position and maximum tolerance on this position. The position shall be given in geographical and Universal Transverse Mercator (UTM) co-ordinates
- name of the rig and rig owner/operator
- time schedule or duration of the operation
- water depth/ground level elevation
- expected rotary table elevation above reference level when drilling unit /equipment is ready to start drilling. For jack-ups the elevation shall be measured from mean sea level (msl)
- estimated total well depth, positions for targets and planned well trajectory. In case a well safety zone (anti-collision) is unintentionally crossed, an amendment along with a risk assessment shall be submitted to the DWEA for approval
- information about directional drilling and a description of method for and maximum vertical interval between measuring the well inclination and direction
- depth to and description of the anticipated geological horizons and eras
- a. stratigraphic column showing and describing anticipated lithology, pore pressure and fracture pressure gradients, planned casing points, estimated reservoir pressure and temperature. Method used for pore pressure and fracture pressure prediction should be stated
- b. representative interpreted seismic sections near the planned well (normally 2 intersecting lines). Location map and location map including offset wells
- c. depth and time structure maps showing primary and secondary prospects as well as time and possibly depth structure maps for other key horizons with a scale of not less than 1:25,000
- d. the velocity functions used in the area
- e. a prospect description of primary and secondary objectives
- abnormal pressures
- a. an evaluation of the possibilities of encountering over-pressured zones with the well in question. This shall be based on seismic data and/or experience from neighbouring wells
- b. a description of methods and procedures to be used for detecting any overpressure in the well
- an evaluation of the possibilities of encountering zones with H2S and other poisonous gases within the well, including description of the methods for detecting and handling of same
- an evaluation of the possibilities of encountering gas pockets in the well in question based on seismic data and experience from neighbouring wells, including the possibility of encountering shallow as well as deep gas pockets
- a list of any other possible significant deviations from the geological/drilling prognosis which may be encountered during the drilling of the well, (e.g. salt zones, swelling clay, high pressured zones) and information on precautions planned in this connection
- a summary sequence of all operations including an estimate of the time required for the different main operations (typical as a time versus depth curve i.e. drilling curve).
The summary shall give a general description of the operations, including information on any special safety related requirements (caused by e.g. possible gas pocket or abnormal pressure) - tentative well schematic for plug and abandonment of the well and for re-establishing the well site. Final plug and abandonment programme must be submitted to DWEA for approval
- information of preparedness and contingency plan for handling H2S and other dangerous gases
- contingency plan related to well operations for use in the event of major accidents or emergency situations regarding health, safety and environment
- information about planned underbalanced drilling operations and its safe performance
Information about the risk assessment – ALARP principle
The programme shall include the risk assessment, cf. section 1.
- assessment of subsurface conditions and identified potential hazards shall be stated
- identified risks shall be recorded and stated and mitigation measures shall be specified and implemented
- residual risks shall be as low as reasonable practicable (ALARP).
Information about casing
The programme shall contain the following:
- diameter of drilled hole
- casing dimension
- grade and type
- planned setting depth for the casing
- strategy for centring of casing, including type of exterior packers and stabilisers, where applicable
- programme for cementing of casing, including type of cement, estimated height of cement behind the casing, and strategy for calculations of necessary volumes of cement
- demonstration of the sufficiency of the casing string strength with regard to burst, collapse, and tension and added safety factor including justification. Reference may be made to company procedure for casing design calculation. In this case the parameters used in the design (pressure, cementing height, mud density etc.) must be stated
- procedure and minimum requirements for testing the formation strength after drilling out the individual casings, including calculations demonstrating that the required formation strength is sufficient for drilling to the next casing setting depth
- precautions to be taken if the required formation strength is not obtained.
Information about the cement programme
The programme shall contain the following:
- detailed information about cement type planned used
- information about the previous casing, dimensions, leak off test (LOT) or formation integrity test (FIT) and the actual casing to be installed and cemented
- information about hole size and drilling mud in the borehole
- information about estimated pressure profile identifying any possible anomalies and top overpressures
- planned height of good cement behind the casing, how this objective is achieved and verified (e.g. CBL, VDL or USIT). Calculations of cement volumes should also be outlined
- information about thickening time, main and tail slurry and pumping time, and all cement additives, and in case of hazardous additives or substances, plans for safe handling
- complete cement testing programme including testing time after cement job, test values, duration, acceptance criteria etc.
Information about well control equipment and blow-out preventer system
- list of all well control equipment available on-board the drilling unit, specifying manufacturer, size, working pressure, maximum pressure, arrangement, specific purpose, function and categorisation (primary or secondary)
- information regarding the control system operating the blow-out preventer stack. A list of the blow-out prevention equipment available on the drill floor ready for mounting on the drill pipe
- procedure for kick control, stating i.e., the data and calculations which by routine are updated to ensure the necessary background for handling emergency situations
- information on how blow-out preventers, measuring equipment, drilling fluid circulation and mixing equipment are expected to be used under such conditions
- programme for function testing of the blow-out preventer and pressure testing of blowout preventer and casing at different stages during the drilling operation. The programme shall also include test intervals, acceptance criteria, maintenance and monitoring
- procedures and plans for well control incidents, including the elimination, minimising, containing, controlling and preventing of a full blow-out. Reference to a well control manual would suffice.
Information about drilling fluid
The programme shall contain the following:
- a detailed description of the types of drilling fluids to be used specifying density and rheological properties etc.
- a detailed description of the components of the drilling fluids. Reference may be made to relevant chemical data sheets
- a detailed description of check equipment and procedures for the drilling fluid or reference to relevant standard
- procedure for monitoring the drilling fluid volume
- a list of the quantities of safety related material (e.g. barite and cement) to be stored on the drilling platform during normal operations and an argumentation for these quantities (cf. section 6.1)
- information about potential borehole instability caused by drilling fluid and formation interaction, and established mitigation plans
- information about environmentally harmful drilling mud discharge to sea while drilling, type, content and quantity.
Information about independent verification
The programme shall include independent well verification, cf. section 4.
Information about logging and measurements
The programme shall contain the following:
- information on types of measurements and logs to be run at various intervals and zones
- programme for taking geological samples, including a coring programme
- tentative programme for planned drill stem testing or test production. Final test production programme shall when applicable be submitted and approved separately.
Information about dispensations
The programme shall include the dispensations from the operator’s own management system/standards and justifications.
If the above information requirements are for some reason not stated in the drilling programme, references shall be made to relevant documents.
Completion programme
In the following, the minimum required documentation to be submitted with regard to completion operations is outlined.
The completion programme shall as a minimum contain the following:
The documentation to be submitted will depend on the type of the chosen lower and upper completion to be installed.
The equipment information shall include type, data specifications, installation, tests and acceptance criteria.
Information about scope of work
The programme shall include the main objectives of the completion.
Information about the well
The programme shall include:
- well description and its current state
- well and reservoir data which could be a potential hazard (CO2, H2S, etc.)
- well schematic prior well operations
- well barriers schematic stating primary and secondary barriers prior well operations
- pore pressure and fracture gradient profile along the wellbore and its stratigraphy
- well geology if not provided with the above profile.
Information about the well operation
The programme shall include:
- detailed well schematic of the proposed solution(s)
- well barriers schematic stating primary and secondary barriers of the proposed solution(s)
- lessons learned from previous completion if available
- detailed programme of the operation including planned tests and their acceptance criteria for all safety and environmental critical elements
- detailed programme of the contingencies if any including planned tests and their acceptance criteria for all safety and environmental critical elements.
Information about the risk assessment – ALARP principle
The programme shall include the risk assessment, cf. section 1.
- assessment of subsurface conditions and identified potential hazards shall be stated, i.e. all potential leak paths to surface or intra formations (crossflows)
- identified risks shall be recorded and stated and mitigation measures shall be specified and implemented
- residual risks shall be as low as reasonable practicable (ALARP).
Information about independent verification
The programme shall include independent well verification, cf. section 4.
Information about completion
The programme shall include information on:
- completion fluids
- wellhead system
- x-mas tree design.
Information about upper completion
The programme shall include information on:
- tubing and hanger
- surface controlled subsurface safety valve and annular safety valve as applicable
- downhole pressure and temperature gauges, chemical injection valves
- Electrical Submersible Pump (ESP), Hydraulic Submersible Pump (HSP) or gas lift valves.
Information about lower completion
The programme shall include information on:
- liner type
- production packer
- flow control components (sliding sleeves, nipples, etc.).
Information about perforation and perforation guns if applicable
- type and data
- safety procedures covering as a minimum safe handling of all devices and equipment planned used, running in and pulling out of hole and firing
- description of the planned explosives, safe handling and shot density
- target intervals and depths.
Information about stimulation, fracturing and acidizing if applicable
- type and data regarding fracturing fluid, proppant and acids, including expected quantities
- safety procedures covering as a minimum safe handling of all equipment intended used, vessel hook-up activities and coordination, running in and pulling out of hole
- pressure, function or inflow tests of valves, fracturing lines and other equipment as applicable, specifying test frequency and acceptance criteria.
Information about dispensations
The programme shall include the dispensations from the operator’s own management system/standards and justifications.
If the above information requirements are for some reason not stated in the completion programme, references shall be made to relevant documents.