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Über dieses Buch

This book is a practical guide to downhole rock sampling and coring concepts, methods, systems, and procedures for practitioners and researchers. Its chapters are based upon years of extensive studies and research about the coring methods and via direct and continuous communication and consultation obtained from various service and operator companies such as Baker Hughes GE, NOV, OMV, and Sandvik.

The contributors discuss the state-of-the-art coring methods and systems (mainly used in the petroleum industry), which include:

· conventional coring;

· wireline continuous coring;

· invasion mitigation coring (low invasion, gel coring, sponge coring);

· jam-detection, anti-jamming, full closure;

· safe-coring and tripping;

· oriented-coring;

· pressure/in-situ coring;

· logging-while-coring;

· motor coring;

· mini-coring;

· coiled Tubing Coring; and

· underbalanced coring.

The contributors provide practical and applicable understanding of the procedures of these coring methods and systems, as well as the specific core barrel components, working mechanisms, and schematics of the tools and processes used. Because Coring Methods and Systems analyses and compares the core barrels used in both petroleum and mining industries, it enhances the communication and may allow knowledge transfer between the two industries.

As core damage is a serious issue during coring and handling jeopardizing correct calibration of exploration data, Coring Methods and Systems has greatly focused on its identification and its mitigation. Therefore, it can be used as an ideal source for geologists, core analysts, and reservoir engineers, to ensure the retrieval of high-quality cores.



Chapter 1. Introduction

Rahman Ashena, Gerhard Thonhauser

Chapter 2. Justified Coring

Rahman Ashena, Gerhard Thonhauser

Chapter 3. Fundamental Coring Methods

Fundamental coring methods fall into three main categories consisting of conventional coring, wireline continuous coring, and sidewall coring. Conventional and wireline continuous methods are applied at the time of drilling and are thus named bottomhole coring. Sidewall coring is used after drilling. These methods are introduced in this chapter (using Anderson 1975; EXLOG/Whittaker 1985; Harrigan and Cole 2011, etc.).
Rahman Ashena, Gerhard Thonhauser

Chapter 4. Types and Components of Core Barrel Assemblies

Rahman Ashena, Gerhard Thonhauser

Chapter 5. Conventional Coring

As mentioned in Chap. 3, conventional coring is a traditional method of taking samples from bottom-hole formations. This method is still the most commonly practiced method in the petroleum industry whereas it is almost never used in the mining industry.
Rahman Ashena, Gerhard Thonhauser

Chapter 6. Wireline Continuous Coring

As discussed in Chap. 5, conventional coring suffers from extremely long tripping times. The whole drilling string must be pulled out of the hole before the whole coring assembly (including inner and outer tube assembly) can be run in the hole. Similarly, following the core-drilling, the coring string must be conventionally pulled out before the drilling string can be run in the hole again to resume drilling. This causes a considerable waste of time during tripping. To address this issue, an alternative method of coring (i.e., wireline continuous coring) has been considered and applied in the petroleum industry (Walker and Millheim 1990; Randolf 1991; Deliac et al. 1991, Bencic et al. 1998; Warren et al. 1998).
Rahman Ashena, Gerhard Thonhauser

Chapter 7. Invasion–Mitigation Coring

One of the basic coring objectives is obtaining core samples with least possible damage to ensure reliable core analysis results. One of the sources of damage is related to mud invasion/chemical.
Rahman Ashena, Gerhard Thonhauser

Chapter 8. Mechanical Core Damage Investigation and Mitigation

To ensure reliable core analysis results, in addition to the invasion-related core damage (discussed in Chap. 7), the least possible mechanical damage should occur to the core. Mechanical core damage is defined as a permanent change in rock properties which is not reversible by restoring the rock back to in situ conditions.
Rahman Ashena, Gerhard Thonhauser

Chapter 9. Jam Mitigation Coring

One of the most common coring problems particularly in critical formations is core jamming (either at the catcher or in the inner tube) and also the risk of core loss or sliding out of the inner tube during pulling out of the hole. As was already listed in Table 5.​1, most of the coring challenges lead to jamming.
Rahman Ashena, Gerhard Thonhauser

Chapter 10. Oriented Coring

Following coring and retrieval of the core sample, knowing its exact orientation with respect to the formation bedding contributes to better understanding the geological structure of the reservoir. Knowing the structure, in turn, helps to identify the most efficient recovery methods. However, this knowledge is not conventionally available unless oriented coring is utilized. Therefore, application of this method is mainly recommended in complex reservoir structures in the drilling and production phases (inferred from Brindley 1988; Laubach and Doherty 1999; Dennis et al. 1987).
Rahman Ashena, Gerhard Thonhauser

Chapter 11. Pressure/In Situ Coring

It was already discussed in Chaps. 7 and 8 that using conventional, non-pressurized coring during tripping, the core may undergo some invasion-related mechanical damage due to the fluid expulsion. This causes some loss of data and inability to recover meaningful core analysis data such as the in situ fluid saturations (inferred from Johns and Lewis 1981; Hyland 1983; Bjorum 2013; Bjorum and Sinclair 2013; Ali et al. 2014; Cerri et al. 2015; Ashena 2017). The capture and characterization of the fluids being expelled out of the core sample during its tripping is a possible solution as it can provide information about the hydrocarbon volume and its properties. To address this issue, pressure/in situ coring has been already introduced in the industry. In this system (combined either with the conventional or wireline operations), at the end of coring, the inner tube assembly containing the core barrel is raised in a closed system to the rig floor, i.e., under its bottom-hole pressure.
Rahman Ashena, Gerhard Thonhauser

Chapter 12. Logging-While-Coring

One of the main challenges during coring, particularly in exploration wells, is the possibility of unidentification of the right coring point/depth. Typically, this can be noticed only at the surface using gamma-ray logging or geology study. In such cases, the retrieved core sample is already obtained from the undesired formation or interval and thus, the success of the operations has been seriously challenged as a lot of money and efforts have been wasted. Facing this challenge, coring may be repeated (this time trying to be in the right depth interval). Ignoring to core and just relying on subsequent wireline logs for formation evaluation is not an option in an exploration well (because the logs would remain uncalibrated without core data and of limited value). Another challenge of coring (and generally formation evaluation) is that coring and wireline logging are taken under different times and thus well and formation conditions causing some adverse mud invasion or mechanical changes, and even depth matching issue (refer to Chap. 8).
Rahman Ashena, Gerhard Thonhauser

Chapter 13. Other Coring Systems

There are some other coring systems, which are not in widespread use, however, they are greatly important for particular applications. These coring systems include motor coring, underbalanced coring, and coil tubing among which motor coring has greater applicability in industry. These will be explained in this chapter.
Rahman Ashena, Gerhard Thonhauser

Chapter 14. Core Handling

When the core barrel containing the core column reaches the surface, the inner tube should be safely handled so that the contained core undergoes the least damage (inferred from Skopec 1992, 1994; Hettema et al. 2002; Shafer 2013; Owens and Evans 2013). To achieve this, in the beginning, a systematic and careful planning is a requirement, which also involves selection of the proper tools in the core barrel (such as disposable inner tubes, NRITS) and the surface handling tools. Next, the proper communication between all the involved, already-trained personnel is required to guarantee the success of the operation.
Rahman Ashena, Gerhard Thonhauser

Chapter 15. Coring Providers and Patents

In the first part of this chapter, detailed specifications and information regarding the dimensions of the core samples, hole size, and working parameters corresponding to some important coring tools, which are provided by the coring providers (both in the petroleum and mining industries) are presented. In the second part of the chapter, some important patent information regarding the current coring systems has been listed.
Rahman Ashena, Gerhard Thonhauser


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