Abstract

Drilling optimization is designed to reduce drilling trouble ime and optimize drilling practices through the use of critical ata interpretation based on a variety of downhole and surface ensors and specialized applications. A recent study for drilling n shallow water shelf in the Gulf of Mexico shows that trouble ime accounts for 25% of rig time. In dollar terms, it is about.S. $1.5 MM per well. Thus, a small reduction of trouble time ould result in tremendous cost saving for the industry. In eneral, a comprehensive drilling optimization should include olutions for: drillstring integrity (such as bit/BHA vibrations), ydraulic management (such as ECD and hole cleaning), and ellbore integrity (such as PP/FG and wellbore collapse odeling). Over the past years, new technologies have made ignificant progress in making drilling more efficient, articularly in improving real-time decision making. The rocess starts with real-time modeling, then proceeds to the ntegration of the real-time modeling and data, and passes inally to the real-time operation centers.

A case study on vibration prevention is presented to illustrate the evolution of new technologies and their impacts to he drilling industry.

Why Drilling Optimization?

Drilling costs are a critical factor in determining the financial returns from an oil and gas investment. Their critical nature is particularly true when operating costs are high and when drilling problems may be likely to occur. Drilling optimization is the key to reduce Non-Productive-Time (NPT) such as stuck pipe, MWD/BHA failures, lost circulation, hole cleaning, and wellbore stability, etc. NPT accounts for approximately 20% of all rig time and can be much higher in difficult fields. A recent NPT study1 on drilling in shallow water shelf in the Gulf of Mexico shows that NPT accounts for 25% of rig time. In dollar terms, NPT is about $1.5 MM per well. Thus, a small reduction of NPT could result in major cost saving for the E&P industry.

In addition to cost reduction, drilling optimization is also a key factor in improving drilling efficiency and safety and in protecting the environment. In some challenging drilling environments (for example, when pore pressure and fracture gradient are close), the wells cannot be drilled without drilling optimization.

For such reasons, therefore, over the last two decades, the E&P industry has adopted many new technologies to enhance drilling optimization. Notable are the use of computer-based instrumentation and data acquisition systems, integrated rig site systems and networks, and Measurement-While-Drilling and Logging-While Drilling (MWD/LWD)2–4

What is Drilling Optimization?

Drilling optimization is a process that employs downhole and surface sensors, computer software, Measurement-While- Drilling (MWD), and experienced expert personnel - all dedicated to reduce trouble time and increase drilling efficiency. Fig. 1 illustrates the traditional optimization process consisting of:

  • pre-run modeling,

  • real-time data measurement and monitoring, and

  • post-run analyses and knowledge management.

At the center of this process are the personnel who are expert in these technologies and who can make recommendations to avoid trouble and improve drilling performance.

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