Larger cores help provide a better understanding of reservoir dynamics

Overview 

When determining the porosity and permeability of a formation, many clients choose to obtain core samples. Magnetic resonance imaging and other types of formation tests are also used, but many producers prefer to look at core samples to get a more detailed understanding of the formation. Halliburton recently developed the HRSCT-B™ rotary sidewall coring tool that provides undamaged samples, without microfractures typical in percussion cores. The tool provides samples that are 1.5-inches in diameter and 2.4-inches in length, more than three times the volume of other tools. It’s rated to withstand temperatures up to 400°F (204°C) and pressures up to 25,000 psi. Cores can be extracted from consolidated clastics and carbonates offshore, conventional and unconventional wells, making the tool one of the most versatile in the industry.

Challenge

The decision to drill a well in a particular field is one of the most important an oil and gas company can make. Producers, geologists and petrophysicists spend hours combing over seismic surveys, magnetic resonance images and more to determine if a well will produce. Numerous core samples are needed to help make these critical decisions. Sidewall coring gives producers a large number of samples, but the size of the samples has historically been a limiting factor. Percussion drilling is commonly used to obtain sidewall cores, but the explosive charge used to shoot barrels into the formation can often damage the core sample, resulting in higher than normal porosities. Rotary sidewall coring tools provide better, undamaged samples. 

Solution

Halliburton recently introduced its latest sidewall coring tool, the HRSCT-B tool. This versatile, reliable coring tool is a new approach for acquiring multiple sidewall core samples. It is efficiently designed to provide a combination of high-speed bit rotation, torque and bit advancement for the best drilling performance. The tool provides undamaged core samples that can easily be acquired in a single run for a range of testing and analysis. Core samples are 1.5 inches in diameter and up to 2.4 inches in length, giving clients a sample more than three times larger than other sidewall coring tools.

The HRSCT-B tool apparatus consists of many intricate parts from the control electronics to the motor drive section to the mandrel section. The bit box is comprised of dozens of gears that work at different speeds, enabling reliable drilling and reducing the possibility of lodging and sticking of the bit in the formation. The mandrel section of the tool can hold up to 60 cores using multiple core separator tubes, enabling a greater number of samples. The tool also operates at 1500 revolutions per minute with a 22-inch torque, enabling faster drilling times. The GUI provides real-time monitoring of bit torque, revolutions and bit advance pressure while drilling the core, giving wellsite geologists an excellent visual aid during the coring process

Result 

In an effort to determine whether or not a well in Southwestern Louisiana would produce, this energy and exploration company elected to use the HRSCT-B tool to retrieve several core samples from a tight sandstone well. The company wanted a detailed look at the porosity and permeability of the formation. 35 core samples – 2.25 inches long – were retrieved from various depths. The cores were obtained in one run downhole and at an average of 3.5 minutes per core, some taking less than 90 seconds to retrieve. This speed and accuracy saved the company time and money.

The accuracy, reliability and versatility of the HRSCT-B tool provided much larger samples and detailed answers about a variety of formations. The tool’s ability to retrieve multiple samples in just one run downhole and the detailed reservoir understanding that producers get from the samples is quickly making it a leader in sidewall coring.