Bits and bottomhole assemblies (BHAs), until recently, have been designed and considered for vertical applications. While inherent design changes and innovations made to BHAs and bits can be applied to both vertical and horizontal wellbores, the industry is targeting horizontal applications. According to Baker Hughes data, of the 1,861 rigs drilling in October 2014, 1,341, or roughly 72%, were horizontal. Ten years earlier, only 10% of the rigs were drilling horizontally. Drilling sideways presents different challenges than drilling vertically.
A biotechnology company from the San Francisco Bay Area is selling a futuristic solution to an old problem: lubricating drill bits grinding though rock. The product is a high-grade lubricant made from algae and is encapsulated in a polymer shell, hence the name Encapso. Coating the oil segregates the lubricant from the drilling fluid until it encounters hard contact or friction during drilling, such as a rotating drill bits on rock. It sounds like a research and development project, but it has been on the market for more than a year and used in more than 40 wells, most of which are horizontal ones drilled in unconventional plays. Cliff Baratta, a senior marketing associate for Encapso at Solazyme, said its lubricant increased the average rate of penetration (ROP) by about 20% in cases in the Williston Basin, where it has been used most often.
More about this topic can be found in Gidley, J.L., Holditch, S.A., Nierode, D.A., and Veatch, R.W. 1990. In their natural state, most oil and gas wells do not produce at their optimum level, but hydraulic fracturing can address multiple challenges to efficient production. Radial flow from the reservoir into the wellbore is not an efficient flow regime. As the fluid approaches the wellbore, it has to pass through successively smaller and smaller areas. If one were to complete the well such that the radial flow changes to nearly linear, then the change in flow pattern will increase well productivity.
In his book The Nature of Technology, W. Brian Arthur remarked, "The story of this century will be about the clash between what technology offers and what we feel comfortable with." A drilling activity employing appropriate equipment and controls where the pressure exerted in the wellbore is intentionally less than the pore pressure in any part of the exposed formations with the intention of bringing formation fluids to the surface. While the benefits of UBD technology include reservoir damage prevention and increases in production and rate of penetration, users can experience discomfort--mainly from operational and safety standpoints, especially offshore--because the well continuously flows to surface while drilling. It can also be expensive, requiring more complex modeling and prediction of compressible drilling fluids behavior during operation. Furthermore, it is not always possible to maintain a continuously underbalanced condition and, since there is no filter cake in the wellbore, any period of overbalance might cause severe damage to the unprotected formation.
This paper reports the completion of a two-lateral well in the Williston basin where produced water (PW), filtered but otherwise untreated, was used throughout the slickwater and crosslinked components of approximately 60 hydraulic-fracturing stages. Proppant was placed successfully in all perforated zones by use of a hybrid design that used 7 million gal of water (of which 2.2 million gal was crosslinked). This paper will concentrate on the development and implementation of a metal-crosslinked fracturing fluid that showed excellent stability. The demand for an economical approach to reuse water from oilfield operations--namely produced, flowback, and nonpotable sources--is not a new concept. In slickwater fracturing, reuse of PW is a solved problem, thanks to the ready availability of synthetic friction reducers that are efficient even in heavy and unpredictable natural brines.
In horizontal and extended-reach wells in which long completions are run into highly deviated or lateral zones, large compression loads arise because of running friction. These loads remain locked in the string when the packer or cement sets. Dissipation of friction caused by string vibrations and movements redistributes these friction loads between the wellhead and the packer or the top of the cement. A numerical approach is presented to calculate the redistributed friction load so that an accurate initial tubing load is implemented in the tubular-stress analysis. The long lateral wells in modern shale developments provide new motivation to better understand and model the effect of friction in casing and tubing design.
Significant progress has been made on physics-based torque-and-drag (T&D) models that can run either offline or in real time. Despite its numerous benefits, real-time T&D analysis is not prevalent because it requires merging real-time and contextual data of dissimilar frequency and quality, along with repeated calibration, the results of which are not easily accessible to the user. In this paper, the application of a real-time T&D model is demonstrated. Traditional electronic drilling recorders (EDRs) are third-party systems that collect rig-sensor data. Major limitations in the operator's ability to fully leverage the potential of this data exist, including issues with rig-sensor-measurement quality and rigsite data-aggregation methods, relatively slow data-sampling rates, and limited interoperability.
Friction can pose major limitations on well length in ultraextended-reach-drilling (ultra‑ERD) well completions. Centralizers coated with diamond-like carbon (DLC) coatings have been developed to provide operational advantages for these ultra-ERD applications. While drilling, pipe can be rotated to release friction, but in completion operations this may not be possible. Although pipe can be air-filled to provide buoyancy, there are many examples of screens and perforated pipe that cannot be floated. The complete paper documents the development, laboratory- and field testing, and lessons learned from a project to evaluate coated centralizers.
This paper presents a coupled 3D fluid-flow and geomechanics simulator developed to model induced seismicity resulting from wastewater injection. The simulator modeled several cases of induced earthquakes with the hope of providing a better understanding of such earthquakes and their dominant causal factors, along with primary mitigation controls. Implementation of rate-and-state friction to model friction weakening and strengthening during fault slip to accurately model earthquake occurrence, and an embedded discrete fracture model to efficiently model fluid flow inside the fault, are among the essential features of the simulator. The complete paper presents results from a combined model that brings together injection physics, reservoir dynamics, and fault physics to explain better the primary controls on induced seismicity. Since 2009, a substantial increase in the number of earthquakes in the central and eastern United States has occurred.
Chandler Engineering has expanded its Model 6500 Friction Flow Loop line with the addition of the Model 6500-M Mini Loop, a patent-pending benchtop unit designed to measure the friction pressure created by different slickwater fracturing fluids. It determines the effects of friction reducers on fracturing fluids over a wide range of pressures, flow rate conditions, and pipe diameters.The unit circulates fluid through a single test section and uses custom software to record and analyze the test data. Proprietary software allows for total operator control over flow rate, test time and temperature for each individual test. The low volume, compact design, and custom software allow for quality control testing.