A new prospect is planned to be drilled by Kenmac Petroleum Corporation on a new licensed Molly field located in the North Sea on Block 14a/b. The tasks involved in well planning are as follows: (a) the estimation and evaluation of pore and fracture pressure and their impact on well planning, (b) a lithology study of the different formations and the steps taken to minimize the occurrence of drilling problems through all different formations, (c) a casing scheme design, (d) a mud programme design for the given well, and (e) a cement type suitable for the application in the given well.
Table of Contents
1. Introduction
1.1 Objectives
2. Pore pressure
2.1 Estimating pore pressure
2.2 Pore pressure importance
2.3 Sources of pore pressure
2.4 Fracture pressure
2.5 Fracture gradient
3. Drilling
3.1 Rate of penetration
3.2 Rock mineralogy
3.3 Lithology study
3.4 Sandstone zone
3.5 Shale zone
3.6 Drilling problems
4. Casing program
4.1 Conductor casing
4.2 Surface casing
4.3 Intermediate casing
4.4 Production casing
4.5 Production tubing
4.6 Casing setting depth
5. Drilling mud
5.1 Basic properties
5.2 Water base mud
5.3 Types of WBM
5.4 Oil base mud
6. Cement
6.1 Cement classification
6.2 Cement selection
7. Conclusion
Objectives and Scope
This report outlines the comprehensive well planning process for the new exploratory well at the Molly field in the North Sea. The primary objective is to develop a safe and efficient drilling design by evaluating geological pressures, selecting appropriate casing schemes, and determining optimal mud and cement programs to mitigate risks associated with borehole stability and abnormal formation pressures.
- Estimation and evaluation of pore and fracture pressures.
- Comprehensive lithology study to identify and mitigate drilling hazards.
- Design of a robust multi-string casing program.
- Formulation of a drilling mud program based on formation requirements.
- Selection of suitable cement types for zonal isolation and structural support.
Auszug aus dem Buch
3.5. Shale zone
When drilling through shales formations the two major problems encountered are the shale sloughing and swelling. Shale instability in a wellbore is attributed to any of the following combination of forces: (i) overburden pressure, (ii) degree of compaction at the formation, (iii) pore pressure in shale exceeding the hydrostatic pressure (iv) tectonic forces and (v) presence of micro fractures along cleavage planes on the clay platelets (Talabani, Chukwu and Hatzignatiou, 1993, p.283).
Brittle (sloughing) shale, Gumbo (plastic) shale and Hydratable (swelling) shale are the major types of shale usually encountered when drilling a borehole. Shales are high compressible sedimentary rocks possessing the ability to absorb water through their lattice structure. They are composed of different minerals such as quartz, feldspar, dolomite, calcite, siderite and gypsum. These minerals are considered inert and are not affected by the drilling fluids. Other minerals such as kaolinite, illite, chlorite, montmorillonite and mixed layer clays absorb water when exposed to water base fluids creating various degree of instability (Talabani, Chukwu and Hatzignatiou, 1993, p.284).
Summary of Chapters
1. Introduction: Presents the scope of the Molly field project and the primary objectives for the exploratory well planning.
2. Pore pressure: Discusses the importance of predicting formation pressures and methods for estimating pore and fracture gradients.
3. Drilling: Examines the challenges of drilling through different lithologies and the factors affecting the rate of penetration and borehole stability.
4. Casing program: Details the design of the casing strings, including conductor, surface, intermediate, and production casing requirements.
5. Drilling mud: Outlines the functions of drilling fluids and compares various types of water-based and oil-based mud systems.
6. Cement: Describes the classification and selection criteria for cement to ensure structural integrity and effective zonal isolation.
7. Conclusion: Summarizes how the integration of geological data and planning parameters results in a robust well design.
Keywords
Well Planning, Molly Field, Pore Pressure, Fracture Gradient, Drilling Mud, Casing Program, Cementation, Shale Stability, North Sea, Lithology, Borehole, Rate of Penetration, Geopressure, Overbalance, Formation Pressure.
Frequently Asked Questions
What is the fundamental goal of this report?
The report serves as a well planning guide for the Kenmac Petroleum Corporation, aiming to design a safe, cost-effective, and technically sound drilling program for the Molly field.
What are the primary technical fields covered?
The core subjects include pore pressure prediction, lithology analysis, casing string design, drilling fluid optimization, and cementation techniques.
What is the key research question addressed?
The research focuses on how to effectively plan a new exploratory well by assessing abnormal pressure zones and potential drilling problems to ensure safe drilling operations.
Which scientific or engineering methods are applied?
The planning utilizes predictive methods for pore pressure, correlations from authors like Hubbert, Willis, and Eaton for fracture gradients, and empirical data for casing and cement selection.
What is the main focus of the main body?
The main body systematically covers the determination of formation pressures, lithological risks (specifically sandstones and shales), casing design based on depth, and the formulation of mud and cement programs.
Which keywords characterize this document?
Key terms include Well Planning, Molly Field, Pore Pressure, Fracture Gradient, Drilling Mud, and Casing Program.
How is the casing scheme designed for the Molly field?
The casing scheme is designed from bottom to top, based on the internal diameter requirements of the production string and the need to protect formations from abnormal pressures.
Why is shale instability a critical focus in this well plan?
Shales present significant risks such as sloughing and swelling, which can lead to pipe sticking and borehole enlargement, necessitating careful mud system selection.
How is the cement selection justified?
Cement classes A, G, and H are chosen based on their performance across a wide range of depths and temperatures, as well as cost-efficiency considerations for the specific Molly field environment.
- Arbeit zitieren
- Ataliba Miguel (Autor:in), 2012, Well Planning at Molly Field, München, GRIN Verlag, https://www.grin.com/document/278037
