Well Planning and Design Ideas for Exploration Well Application

Module Learning Outcomes Assessed:

1. Evaluate the technology required for drilling a well, and be able to calculate when drilling a horizontal well would be advantageous. Comprehend the basics of Multi-Lateral technology

2. Develop a bit, mud, casing and cement program with regard to production flow rates and basic design principles.

Task and Mark distribution:

Submit WELL PLANNING AND DESIGN IDEAS to be considered in the preparation of a (vertical) exploration well application. One of the oil/gas fields listed on the website of the Norwegian Petroleum Directorate will be assigned to you, so that you can collect data for your field

Base all your design ideas/considerations on the available data from the location. State clearly any assumptions you have made to arrive at your design idea. Also support your consideration where necessary.

                                                    Marking Scheme

Well planning and design

1. Defining Well Objectives ( 6 marks)

Based on the information provided, make a justification for drilling this well- state clearly what the objective is, and what depth the objective will be found at.  How many days do you predict that it will take to drill this well?

2. Obtaining Consent to Drill from authorities (10 marks)

You are expected to outline the steps involved in obtaining drilling consent. Since this well is to be drilled in the Norwegian Sector of the North Sea, then you need to identify the key authorities involved in this process.  NOTE: This is not the same as applying for an exploration or production licence!

3. Establishment of subsurface pressure regimes,  and  presenting the formation pore pressures  for your allocated field graphically (10 marks)

   Formations are said to have hydrostatic pressures. Higher pressures can be

   encountered for several reasons such as:

· artesian wells

· gas caps

· salt beds

· sediment compression

· mineralisation

· surcharged formations

formations can also be sub-hydrostatic due to:

· depletion

· faulting

· artesian wells

Knowledge of local and regional geology, as well as well data from nearby wells,  will give the Drilling Engineer a working pore pressure prediction that he/she can use for their calculations.

Please present the formation pore pressure data in a depth vs pressure plot

that also references against the rock formations  anticipated at any particular depth.

4. Establishment of formation fracture gradients    (10 marks)

As with formation pressures, prediction/ assumptions can be based on anticipated geology and outstep well records. Most rock of a certain type will exhibit typical characteristics. This can be used to assist in fracture gradient estimation. It is vital to have an accurate assessment of North Sea area based on existing literature so that the casing design can be done in an effective manner.

Again, please present the formation fracture gradients in a depth vs pressure plot that also references the anticipated geology in your allocated area.

Driling Programme Preparation

Design criteria

5.    Casing design and selecting the casing seats (10 marks)

A typical offshore well may have a 30 inch conductor, a 20 inch surface casing, 13 3/8 inch and 95/8 inch intermediate casing and a 7 inch production liner. Although the above is a common arrangement, there is a multitude of different combinations of casing sizes which the operators may choose to run if he desires and if the casing design allows it.

6.    Wellhead selection (4 marks)

Having completed the casing design, you have all the information required to allow you to select a wellhead. The wellhead must be of the correct pressure rating, designed for the desired service (H2S or whatever) and be capable of accommodating all designed and contingent casing sizes. In practice this comes down to a choice between a few major manufacturers products. The final selection will probably come down to the ease of operation, cost and the operator’s personal preferences. Having selected a wellhead, its specification should be included in the he Drilling Programme along with a sectional view of its component stacks up.

7. BOP requirements (4 marks)

The BOP requirements for a given well will depend on company policy and anticipated bottom hole pressures. Surface holes have either no BOP requirement, or will need to use a divertor. This will be specified in this section. The information should be presented in a format such as:

 Provide source of data used here

8.    Cementing programme (10 marks)

Cement is used for zonal isolation in the well. The effectiveness of this zonal isolation depends on three main factors all of which must be considered at the planning stage.

1. Slurry design

2. Casing accessories selection if required for the area

3. Displacement methods

9.    Mud programme (10 marks)

In practice, mud programming can be broken down as follows:

1. Determination of mud weight requirement to maintain primary well control.

2. Confirmation that this mud weight does not exceed formation strengths when considered in a dynamic (i.e., circulated) mode.

3. Analysis of formations to be drilled and the likely reaction of these to the available drilling fluids alternatives. Using this information to select a basic mud type.

10.     Bit programme (6 marks)

Bit selection -To select a bit the following factors are considered:

1. formation, drill ability and characteristics

2. mud system in use

3. directional implications

4. bit drive methods

5. availability and cost

11. Evaluation requirements (5 marks)

In this part of the programme, outline what you will consider requirements necessary to meet the well objectives and this should be formatted as follows:

1. Drilling log requirements

2. Mud logging requirements:

3. Coring requirements:

4. MWD requirements:

12. Operational procedures and time depth graph construction (5 marks)

The degree of detail required in the operational procedures part of the Drilling Programme is closely related to what a comprehensive Drilling Operations Manual will provide. It is a step-by-step guide to what has to be done in the well.

The Time Depth Graph is a tool used to show the expected well status at any time from spud to completion of plug back and abandon. To construct a Time Depth Graph you have to make assumptions and estimates must be made.

The Time Depth Graph uses time along the x-axis usually in days and depth along the y-axis with zero depth at the upper end of the axis. See sample provided in class.

13.     Authorization for expenditure (10 marks)

Capture all the significant costs here. Don’t forget  rig hire, personnel costs, casing and drill-pipe costs, drill bits, BOP, cement, drilling fluids ……………..etc.  etc.

Notes:

1. For support and advice on this students can contact Centre for Academic Writing (CAW).

2. Please notify your registry course support team and module leader for disability support.

3. Any student requiring an extension or deferral should follow the university process as outlined here.

4. The University cannot take responsibility for any coursework lost or corrupted on disks, laptops or personal computer. Students should therefore regularly back-up any work and are advised to save it on the University system.

5. If there are technical or performance issues that prevent students submitting coursework through the online coursework submission system on the day of a coursework deadline, an appropriate extension to the coursework submission deadline will be agreed. This extension will normally be 24 hours or the next working day if the deadline falls on a Friday or over the weekend period. This will be communicated via your Module Leader.

6.  Assignments that are more than 10% over the word limit will result in a deduction of 10% of the mark i.e. a mark of 60% will lead to a reduction of 6% to 54%. The word limit includes quotations, but excludes the  reference list and tables.

7. You are encouraged to check the originality of your work by using the draft Turnitin links on your Moodle Web.

8. Collusion between students (where sections of your work are similar to the work submitted by other students in this or previous module cohorts) is taken extremely seriously. Plagiarism (where material is copied from another source without being attributed correctly) is also a serious offence. Both will be reported to the Academic Conduct Panel. This applies to both coursework and exam answers.

9. A marked difference between your writing style, knowledge and skill level demonstrated in class discussion, any test conditions and that demonstrated in a coursework assignment may result in you having to undertake a Viva Voce in order to prove the coursework assignment is entirely your own work.

10. RESIT COURSEWORK: If you get less than 40% in this assignment you will need to resit in the next semester. For the re-assessment of this coursework, you should improve your initial attempt to a satisfactory level using the feedback provided (on CU Moodle). Your resit attempt should address all feedback comments which may include conducting further analysis, incorporating additional literature, strengthening your academic argument and improving the format and/or structure of your work.

11. You must not submit work for assessment that you have already submitted (partially or in full), either for your current course or for another qualification of this university, unless this is specifically provided for in your assignment brief or specific course or module information. Where earlier work by you is citable, ie. it has already been published/submitted, you must reference it clearly. Identical pieces of work submitted concurrently will also be considered to be self-plagiarism.

0-39

40-49

50-59

60-69

70+

80+

Work mainly incomplete and /or weaknesses in most areas  

Most elements completed; weaknesses outweigh strengths

Most elements are strong, minor weaknesses

Strengths in all elements

Most work exceeds the standard expected

All work substantially exceeds the standard expected