Latest Oil and Gas News Russia

Alexei Govzitch, Area Manager for Smith International

Peter Frew, Area Manager for Russia, Ukraine & Belorussia, ReedHycalog

Bruno Cuillier, Eastern Hemisphere PDC Production Manager, Varel International


1. Every bit manufacturer has its own process of design - what new design techniques are being used to maximise bit quality.

SMITH: Smith Bits uses its unique and patented IDEAS (Integrated Dynamic Engineering Analysis System) software as a bit design platform.

Developed initially for roller cone bits in 1996, it then became the platform for PDC bit design in 2003. The system is the most accurate and advanced simulation software currently used for drill bit design in the petroleum industry. IDEAS is a timed-based, 3-D modeling tool that uses finite element analysis to accurately simulate and predict the mechanical behavior of the entire drilling system. The model is extremely sensitive to the data that is entered for each analysis, and the analysis allows the performance of a new bit design to be predicted before the prototype is run. It also takes into account the forces at rock-cutter interface in numerous lithologies, the mechanical properties of the entire drill string, the exact drive system (PDM, point-the-bit or push-the-bit RSS, turbines, etc.) and the well profile.

Even though this system is in its 11th year of use, the model is continually being refined and updated to include new lithology information and the latest downhole tools. This allows IDEAS to stand alone as the most powerful engineering design tool in the oil industry.

REED: ReedHycalog, as one of the worlds leading suppliers of drilling bits, understands what factors lead to the wear and damage seen on bits when they are used in most drilling applications. Engineers utilise this understanding to incorporate features that address specific wear characteristics in order to maximise performance of the bit.

For example, we have recently developed a design programme that can objectively analyse lateral stability of PDC bits, a critical factor to ensure excellent bit durability.

Similar modelling programmes are used for roller cone bits. Additionally we use novel techniques in manufacturing, moving away from the standard materials, for example, into more exotic types that offer improved abrasion resistance on the cone, such as our TuffCutterTM soft formation tooth bit series.

There is a continuous cycle of improvement within the drill bit industry. As we seek to use bits to drill longer and more technologically advanced wells we require bits that are capable of maximising performance and so reduce drilling costs to the operators.

VAREL: When Varel engineers design a new drill bit the tools utilized are proprietary incorporating a "full numerical chain" where the human factor is minimized. The Varel process includes GeoScience, SPOT, Pro-E, CFD, and Pro-E manufacturing.

GeoScience examines the rock to be drilled calculating UCS [unconfined compressive strength], hardness, abrasiveness, drilling factor and wear index while determining formation type and effective porosity. All of these formation characteristics contribute to bit performance and are input into SPOT, our software simulator for the optimization of drill bits. SPOT considers the following bit attributes during design: axial and lateral displacement, imbalance force, directional behavior (i.e., steerability plus walk), cutter wear, ROP as cutters wear, and bit behavior based on dynamic factors. Pro-E is the modeling tool we use to help with visual analysis of the completed bit design. The completed Pro-E design is then imported into CFD where the fluid flow is modeled and nozzle orientation is checked to ensure proper cleaning of the bit face and cooling of the cutting structure. Finally, Pro-E manufacturing then supplies the necessary files to various machining centers to guarantee that designed accuracy is met in our finished product.

2. With ConocoPhillips working closely with Lukoil drilling several horizontal wells in Western Siberia, they are looking to increase the overall ROP. What improvements can be made in bit design in order to maximize the ROP, and what guarantees can be made?

SMITH: Again, using IDEAS allows Smith to design an optimum bit (blade count, cutter size, cutter backrake angles, hydraulic configuration etc.) for a specific application.

The outputs generated by the IDEAS model will give an indication of the expected performance, for example relative ROP (different bit designs) and the magnitude and type of vibration.

REED: Bit design is essentially a process of balancing the four basic criteria of bit performance: ROP, Durability, Stability and Steerability. These four criteria or indices are mutually interdependent. Sometimes there are contradictory needs in order for a particular bit to meet all the objectives of the Operator. For example, producing a more aggressive PDC bit is relatively easy to accomplish by such means as reducing back rake, reducing blade count, increasing cutter size, etc. However, in doing so, there is a strong possibility that durability of the bit will be compromised.

It should be remembered that the simple cost per metre equation that is widely used consists primarily of rig cost multiplied by number of hours, both drilling and tripping, divided by the meterage drilled. Should a bit be capable of drilling extremely fast yet not make the required section then the total costs of that section using two "fast" bits may be greater than using a slower, yet more durable, bit. The converse is also true in that sometimes using two bits may be more cost-effective than attempting to drill a section in a single pass.

It should also be pointed out that the bit is only one component in the drilling system that extends from the bit to the rig floor. The speed of a system is limited to that of the slowest or least efficient component. If the ROP is increased without a corresponding improvement in, for example, hole and mud cleaning capabilities, then benefits will not be sustainable.

VAREL: When designing drill bits, it is most effective when the operator and the bit company can have a good relationship that consists of sharing data and expectations. As outlined earlier, Varel utilizes several proprietary tools to maximize drill bit performance. In the instance provided, it is our recommendation to acquire data about the rock lithology, rock hardness, information about the capabilities of the RSS equipment so that we can design the right bit for the specific application. There are a variety of RSS tools available today, and each operates differently and influences bit performance differently. As a company we have developed an effective process for optimizing our bits with the different RSS systems.

3. What effect does the influence of the mud density and viscosity have to the ROP for PDC bits?

SMITH: The greater the differential between the mud weight and the pore pressure (i.e. the degree of overbalance), the slower the ROP will be.

It has also been observed that under certain hydraulic regimes and geological circumstances, a "plastic shale" phenomena can be induced which will adversely affect ROP.

Rheological properties such as viscosity will obviously impact on the cuttings carrying capacity and will result in pressure losses (and thus the Equivalent Circulating Density).

REED: Of these two factors mud density is the most important for bit performance. As the specific gravity is defined by the expected pressures within the well bit companies often have to recommend bits that can compensate for the loss of ROP that comes about when the overpressure, i.e. the differential between borehole and in-situ formation pressure, is increased.

There is only an apparent increase in rock strength, so in order to compensate for the drop in ROP lighter set bits can be utilized which increase the load per cutter and the depth of penetration into the formation.

4. Does well pressure and temperature also affect bit performance?

SMITH: Obviously with extremely high pore pressures, correspondingly high mud weights will have to be used and this is why a robust and efficient pressure equalisation system has to be incorporated in the bearing/seal packages of roller cone designs.

Depending on the geothermal gradient encountered, the properties of the elastomeric seals in roller cones bits can be adversely affected.

With this in mind, rollercone seal material may have to be modified in high temperature environments.

REED: Temperature has little effect on bit performance except where very high temperatures may affect elastomers in roller cone products.

Typically if the formation pressure increases then to prevent influx of well bore fluids the mud weight will be increased. This has the effect of reducing ROP's of drill bits as above.

VAREL: Bottomhole well pressures require higher density drilling fluids that adversely affect the ROP. But this effect occurs more so on roller cone bits than PDC bits because the high temperatures can effect life of the bearings and seals. In terms of the effects mud weights have on PDC bits, water-based muds can negatively effect performance more so than oil-based muds. This is due the chemistry of the water-based mud and how it lubricates and cools the cutters.

5. We hear a lot about bits being designed for specific fields - is it possible to tailor a bit to each and every field, and is this cost effective?

SMITH: Yes, it is possible to tailor a bit to each and every field. The cost effectiveness of this would be determined by the size of the field and how many bits are required.

As we all understand however, it does not make a lot of sense to be designing different bit every time a well is drilled.

REED: Yes, it is possible to tailor a bit to optimise performance in a particular field. However, in order to economically justify designing and manufacturing bits for specific applications then there needs to be a fundamental change in the relationship between the Operator as customer and the Bit Supplier. The relationship must change to become much more a partnership with the Bit Supplier being involved in the wells right from initial planning stages. Focusing on total drilling cost rather than bit cost is critical to making sound decisions to maximise drilling efficiency.

In this regard the circular process of planning, execution, evaluation and analysis becomes vitally important so that the desire for continuing improvement in bit performance can be achieved.

VAREL: It is part of Varel's culture and design philosophy to optimize bit performance by organizing our workflow processes so that we are an effective solutions provider for our customers. We know customization has a profound effect on bit optimization. So, as outlined earlier, we have specific design and manufacturing processes that incorporate field data and utilize proprietary tools. During these processes, we work closely with the customer to evaluate rock lithology and examine the formation characteristics and review the proposed rig equipment. Using this information Varel engineers can design a drill bit for the specific application. This process maximizes bit optimization and performance and reduces total drilling costs.

6. As casing whilst drilling becomes more common, what bits are available to ensure maximum ROP and directional stability?

SMITH: PDC bits are available through different manufacturers for this technology.

REED: In general terms bit companies will attempt to match the bit and the application wherever possible. The type of well tubular will be factored into the design of the bit whether it be Casing While Drilling, Coiled Tubing Drilling or conventional tubulars.

7. How do you see bits changing over the next 10-20 years?

SMITH: Some significant innovations in material science and materials engineering have resulted in PDC bits encroaching further into what were previously considered rollercone applications.

I would expect these innovations to continue, partly due to the fact that the petroleum drill bit industry is so competitive, and we will see the envelope of application for both rollercone and PDC bits expanding. With this in mind, Smith Bits continues to invest a significant sum of money in research and development.

REED: Many of us in the industry remember the first trials of PDC bits and their successes and failures. It is interesting to note how far we have come technologically with that design concept, although it was largely based on the old drag bits of one hundred years ago.

Various novel means of drilling rock are being trialled throughout the world and I feel that some of those features will be incorporated into existing bit designs to improve performance.

VAREL: Advances in raw materials and manufacturing methods, in our opinion, will reduce the cost and production time of drill bits. This includes everything from advances in PDC cutter technology to new lithology evaluation tools to improved drill bit design tools to new manufacturing equipment. Also, the demands from the industry, in terms of different well profiles and advances in drilling rig technology and RSS systems will impact the drill bit business. Advances in realtime drilling data and analysis will be something to watch, as well, as they could have a positive effective on drill bit optimization. As a company, Varel will continue to evaluate such advancements and will adopt those that improve product effectiveness, reduce production time and reduce customer costs.

8. With such bit and supplier choice, how does a company start the bit selection process?

SMITH: From an operator standpoint, bit selection would typically be based on proven track record, experience in the area (or similar applications), understanding of the application, the range of technology available and the level of technical support offered.

REED: The primary driver when choosing bits is to reduce the overall costs of drilling the well to the appropriate downhole location. In order to do this successfully the operator must look at the entire drilling process and effectively rank the bit characteristics required to achieve the well objectives and reduce the overall cost within the confines of the operation.

Understanding of the four primary indices; ROP, Durability, Stability and Steerability, of bit design will provide a suitable starting point for effective bit selection when this process is performed as part of the planning of the well from spud to TD. Adequate planning is probably the most important component that will improve efficiency and reduce overall costs. It is worth stating that the entire rig is organised so that the bit can drill effectively but to obtain maximum performance the knowledgeable staff of Bit Suppliers should be consulted in good time to bring their experience to bear in order to push the envelop of performance even further.

Speaking purely for ReedHycalog we maintain various databases from which we can extract useful information that, should it be utilised in the planning of a well, would lead to considerable cost savings. Furthermore using on-site supervision and dedicated Engineering staff we are able to "close the loop" by providing after sales feedback which can be then used to improve performance on subsequent wells.

VAREL: Bit selection is based on data. The operator/customer has expectations for the project. Such expectations include total drilling days, total drilling costs, completions costs, to name a few. Historical bit performance in the current or nearby field is helpful information, too. Using this information, bit companies, like Varel, work with customer to understand the rig capabilities and project objectives to optimize bit performance. Then, as outlined earlier, Varel uses all of this data and our proprietary design tools to design and manufacture the right bit for the specific application. The result is an optimized drill bit which can reduce our customers' total drilling costs.

9. With the quality of rigs in the FSU are you really seeing the performance from the Western bits or are you wasting a lot of the benefits they can provide?

SMITH: Yes, we are seeing the performance and yes, we under utilize the technology sometimes due to the lack of rig capabilities (flow rate, WOB, torque, drilling information recorders, etc.).

One unfortunate thing is that sometimes we have to design a bit to be compatible with the rig more than the lithology.

REED: ReedHycalog are contracted to supply bits for complete wells on fixed sum payment terms for several Operators. As we take on some of the risks inherent in the drilling we have analysed which bits provide the best return on investment for us whilst drilling these wells. We will use a mixture of Russian and Western manufactured bits, chosen according to their relative merits.

As stated above the bit is part of the drilling system and whilst the system will only operate at the speed of its slowest component, the entire system will fail when the weakest component fails. It then becomes a sort of risk analysis to ascertain the appropriate equipment levels for all the components in the system.

It is generally accepted throughout the industry that equipment levels are rising within Russia, but there is further progress to be made and only when the entire system is at a high level will maximum benefits be gained from any technologically advanced product.

VAREL: To maximize drill bit optimization and performance, Varel designs the drill bit cutting structure using tools which consider the rock mechanics and the available rig power. Well objectives need to be clearly defined at the beginning to better understand the goals. Understanding all of this, Varel engineers can match the right bit for the application and help the operator maximize bit performance and reduce their costs.

Labels: bits, Drill bit, Reedhycalog, Russia, Smith International, Varel

posted by The Rogtec Team @ 14:30 

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