Downhole Data Research Articles

Study of Hydraulic Fracturing Real-time Evaluation Technology

Hydraulic fracturing real-time evaluation technology provides an effective way to understand formation and fracturing, assess the quality of fracturing construct, and ensure the safety of fracturing construction. In this paper, com- bined with numerical simulation and data analysis, a new 3D model of real-time fracture extension is established on the basis of the theories of fluid dynamics, linear elastic fracture mechanics and computational mathematics. This model satis- fies the requirement of hydraulic fracturing real-time with the advantage of simple in form, precise and fast in computa- tion. Considering the influence of proppant on the friction calculation of sand mixed fluids, a wellbore flow model is de- veloped, which is more widely used and makes it no need of down-hole data acquisition. The authors also study the relat- ed data acquisition technology, and set three ways of acquiring data, which could realize the real-time acquisition of field data. In order to match the real wellhead pressure, an optimizing model and its automatic fitting methods for assessing formation and hydraulic fracturing parameters at real time is proposed. The parameters include fluid rheological proper- ties, leakage levels with dynamic changes, fracture geometry and proppant distribution and migration. The application in Xinjiang oilfield in China showed that the presented technology can satisfy the requirements of fracturing, analyze and evaluate fracturing construction quality and guide fracturing design effectively.

Optimal Energy Transfer Pipe Arrangement for Acoustic Drill String Telemetry

Drill string acoustic telemetry is an effective transmission method to retrieve downhole data. Finite-difference simulations produce the comb-filter-like channel response (patterns of pass bands and stop bands) due to the presence of coupling joints in the metallic drill string. Practical pipes used for drilling deep wells have slight variation in length. The selection and arrangement of downhole pipes is important for improving the transmission efficiency of extensional waves transmitted through the drill string. Downhole drill string channel is studied using the transmission coefficients calculated from the transmission matrix method, and the resultant transfer function produces identical results similar to the finite-difference simulations. Reciprocity of the drill string structure is proved by comparing the pass band responses using the ascend-only (AO) and descend-only pipe arrangements. Transferred energies calculated up to 180 pipes of random length at the end of the drill strings using transmission coefficients for the three different pipe arrangements, namely, AO, descend-then-ascend, and ascend-then-descend (ATD), are compared to find the optimal pipe arrangement for single measurement. For the situations when pipes are distributed in sets, multiple measurements are required. In this paper, two sets of AO and two sets of ATD arrangements are analyzed for multiple measurements. ATD and $n$ xATD arrangements are proposed as optimal pipe arrangements to produce the best possible telemetry performance in terms of optimal acoustic energy transfer via one- and two-way acoustic communication for single and multiple measurements, respectively.

Application of simulated annealing optimization algorithm to optimal operation of intelligent well completions in an offshore oil reservoir

The latest intelligent fields include intelligent well completions capable of collecting downhole data, which allow the operator to selectively control completion intervals throughout the life of a reservoir. Performance can be monitored and optimized in real time and operations can be adjusted remotely using downhole equipment. To quantify and develop this potential, we deigned an algorithm-based system which is capable of optimizing intelligent well control to decide on whether or not to utilize intelligent well technology. Simulated annealing algorithm was used for obtaining an optimum control strategy and determining an operation that maximizes the net present value (NPV). In this article, we used more than 4,000 simulation runs which were performed automatically in a reservoir simulator to optimize a cyclic production scenario with intelligent well completions. The intelligent wells were equipped with on/off inflow control valves in each zone, which were opened and closed sequentially to maximize the oil rate while not exceeding limits for water production. The results show that the application of simulated annealing algorithm for optimization of intelligent well technology culminates in an increase in the NPV through 14 % increase in cumulative oil production and a significant reduction in water production.

Numerical model of the Habanero geothermal reservoir, Australia

A TOUGH2 reservoir model has been developed for the Habanero enhanced geothermal system (EGS), located in the Cooper Basin, Australia. The reservoir, interpreted to be the sub-horizontal Habanero fault, was defined by the extent of the stimulated seismic cloud. A 1D natural state model was used first to calibrate the rock thermal properties, heat generation and the heat flux at the base of the model. The temperature distribution was matched against measured down-hole data from well Habanero 1. A 3D model was then developed with 9 horizontal layers and aligned along an impermeable eastern boundary fault. Gravity potentially plays an important role so the model was tilted to the west-south-west. Since the fine 72,000 cell model only extends to 20km2 whilst the reservoir rock (Innamincka Granite) extends to over ∼1000km2, Dirichlet boundary condition (large block volumes) was used for the sides with closed boundaries at the top and bottom. These large cells simulate the extension of the reservoir beyond the limited dimensions of the basic model. The permeability of the stimulated and mud damaged zones was calibrated using stable closed-loop (doublet) production and injection history data. The porosity was calibrated by simulating the two tracer tests carried out at Habanero. In preparing future production forecasts, four different well layouts were considered: staggered line drive (SLD); inverted 4-spot, regular 5-spot and east-west SLD. For each scenario, closed-loop circulation at 25, 35 and 45kg/s per well was modeled for a production period of 20 years. The well patterns were stretched to about the maximum well separation available within the existing seismic cloud, as well as hypothetical seismic clouds. For a larger-scale development plan the best outcome was chosen by balancing short-term temperature against long-term extensibility. The results within the existing seismic cloud indicate the 4-spot layout as the most optimum. The best temperature performance is obtained from an extended seismic cloud when using an east-west SLD.

Controls on disseminated PGE–Cu–Ni sulfide mineralization within the Rietfontein deposit, Eastern Limb, Bushveld Complex, South Africa: Implications for the formation of contact-type magmatic sulfide deposits

The Rietfontein platinum group element (PGE)–Cu–Ni sulfide deposit of the Eastern Limb of the Bushveld Complex hosts disseminated contact-style mineralization that is similar to other economic magmatic sulfide deposits in marginal settings within the complex. The mineralization at Rietfontein consists of disseminated PGE-bearing base metal sulfides that are preferentially located at the contact between a distinct package of marginal norites overlain by a thick heterogeneous unit dominated by gabbronorites with lesser norites and ultramafic rocks. Down-hole composite data and metal scatterplots indicate that the PGE correlate well with Ni, Cu and S and that only minor metal remobilization has taken place within the basal norite sequence. Plots of (Nb/Th)PM vs. (Th/Yb)PM indicate that the melts that formed the Rietfontein intrusive sequence were strongly crustally contaminated prior to emplacement at Rietfontein, whereas inverse relationships between PGE tenors and S/Se ratios indicate that these magmas assimilated crustal S, causing S-saturation and the formation of immiscible sulfides under high R-factor conditions that generated high PGE tenor sulfides. Reverse zoning of cumulus minerals at Rietfontein suggests that fresh primitive melts were introduced to a partially fractionated staging chamber. The introduction of new magmas into the chamber caused overpressure and the forced evacuation of the contents of the chamber, leading to the emplacement of the existing magmas within the staging chamber at Rietfontein in two separate pulses. The first pulse of magma contained late-formed cumulus phases, including low Mg# orthopyroxene and plagioclase, was emplaced between footwall unreactive and S-poor Pretoria Group quartzites and a hangingwall sequence of Rooiberg Group felsites, and was rapidly chilled to form the basal norite sequence at Rietfontein. The second pulse of magma contained early formed cumulus phases, including olivine, chromite, and high Mg# orthopyroxene, and was emplaced above the chilled norite sequence as a crystal mush to form gabbronorites and ultramafic rocks. This second pulse of magma also contained PGE-bearing base metal sulfides that accumulated at the contact between this second batch of magma and the already chilled basal norite sequence. The formation of Platreef-type mineralization outside of the Northern Limb of the Bushveld Complex confirms there are a number of areas within the Bushveld Complex that are prospective for this style of mineralization.

Source reverberations, near-surface resonances, or Q? Comment on “The peak frequency of direct waves for microseismic events” (Leo Eisner, Davide Gei, Miroslav Hallo, Ivo Opršal, and Mohammed Y. Ali, Geophysics, 78, no. 6, A45–A49)

In a recent Geophysics Letter, Eisner et al. (2013) measure peak frequencies in velocity spectra of direct waves from microseismic events. The authors interpret these peak frequencies as being caused by attenuation and use them for estimating the effective Q -factor of the medium. Nevertheless, I point out a significant problem with these results, namely, that the authors’ model for the earthquake source is not accurate enough to allow the determination of Q for the surrounding medium. This can be seen by considering the following question: Do the Q values reported in Eisner et al. (2013) characterize the medium, the source model, or the spectral data for direct arrivals? Eisner et al. (2013) assume the first of these answers to be correct; however, careful analysis shows that the correct answer is actually the last one. In answering the above question, note that the Q and t * values measured by this method are not unique physical properties of the medium because they change whenever a different source model is used. The flat plateau at f f c in the Eisner et al. (2013) source spectrum is unrealistic, and yet this plateau is the principal tool of the authors’ method for Q estimation. If we use, for example, Brune’s (1970) model as a more accurate one, then the Q would be much larger than the values reported by Eisner et al. (2013) (see the subsection “Meaning of Q ” below). Thus, the inferred Q s follow from the assumed source model. However, these Q values still cannot be viewed as corrections to the source model because even after these corrections, the model fits the observations very poorly (see the subsection “Data fit”). Therefore, the Q values proposed by Eisner et al. (2013) can only be interpreted as the observed spectral-peak frequencies heuristically multiplied by traveltimes: …

Reservoir monitoring of steam‐assisted gravity drainage using borehole measurements

ABSTRACTThis paper presents the results from a research project focusing on permanent cross‐well geophysical methods for reservoir monitoring during steam‐assisted gravity drainage. A feasibility study indicated detectable differences in seismic and electrical reservoir properties based on expected changes in temperature and fluid saturation during the production of extra heavy oil. As a result of this, a permanent cross‐well system was installed at the Leismer Demonstration Area, located in the Athabasca Oil Sands region in Alberta, Canada. Baseline data sets, including cross‐well seismic, three‐dimensional vertical seismic profiling and cross‐well electrical resistivity tomography, have been acquired. Comparisons between conventional surface seismic and downhole seismic data show an increase in resolution and frequency content as expected. Steam‐assisted gravity drainage‐induced time‐lapse effects are clearly visible in the 3D vertical seismic profiling and electrical resistivity tomography data sets, even after a few months of oil production. In general, the 3D vertical seismic profiling images show a higher resolution than the surface seismic data, in particular when dealing with vertical positioning of the time‐lapse events. The electrical resistivity tomography baseline shows clear separation between zones of high and low electrical resistivity, and during 23 months of electrical resistivity tomography measurements the maximum reduction of resistivity is 85%. Time‐lapse observations from acoustic and electrical borehole data correspond well, and are also supported by temperature measurements in the two observation wells. Emerging technologies, updated models, improved flexibility, and reduced costs will allow future reservoir monitoring with surface and borehole data in combination, or even with borehole data exclusively.

Coal-Seam-Gas Reservoir Surveillance—Extracting Value From Suspended Coreholes, Surat Basin, Queensland, Australia

Summary In 2009, QGC (a BG Group company) began developing coal-seam-gas (CSG) feedstock for its new liquefied-natural-gas (LNG) plant and required a subsurface model and field-development plan to underpin the investment case for the project. Fundamental to the modeling process was acquiring appropriate data to calibrate subsurface models and enhance confidence in their predictive quality. As part of an integrated reservoir-surveillance strategy, specific pressure- and temperature-monitoring wells were required. This paper describes the successful laboratory and field implementation of an innovative completion technique that converts suspended coreholes into reservoir- and aquifer-monitoring wells. The coreholes are re-entered, and vibrating wire piezometers attached to capillary coiled tubing are positioned and cemented in place alongside selected reservoir intervals. The well is then “plugged and abandoned,” and the lease is remediated to leave only a small surface footprint for the data logger and telemetry. The cement is effectively impermeable to fluid movement, but possesses sufficient permeability to transmit reservoir pore pressure to an adjacent piezometer. Recompletion of coreholes provides a cost-effective means of acquiring valuable downhole data while eliminating the need to drill a well specifically for monitoring in the same vicinity. Data gathered over the reservoir interval (the Walloon Coal Measures) can inform and help resolve reservoir properties on a regional scale, enhance understanding of the contribution to flow, and provide data points to pressure match a reservoir model. Data gathered over the aquifers within Springbok sandstone and Gubbermunda sandstone enable estimates of any CSG-production effects on groundwater.

OFDM Wireless Downhole Transmission Systems and Proposed SLM Method for PAPR Reduction

At present, mud pulse transmission systems are widely used in downhole data transmission. But the systems are very low in transmission efficiency, only 5-10 bits/s, with very large anti-inter-symbol-interference (ISI). It cannot meet high requirements for high-speed transmission of modern logging system. The development of communication technology has laid some foundation for this requirement. For this purpose, the Orthogonal Frequency Division Multiplexing (OFDM) Wireless Downhole Transmission Systems are proposed for the first time because of their high transmission rate, anti-inter-symbol-interference (ISI), and high spectral efficiency, etc. Due to non-linear power amplifier (PA) of logging systems with limited dynamic range, the drawbacks of high peak-average power ratio (PAPR) may outweigh all the potential benefits of OFDM wireless downhole transmission systems. Selective mapping (SLM) method can reduce the PAPR of OFDM logging signals without distortion. But at the receiver, the conventional SLM method needs exact bits of side information (SI) to recover the data signal. The probability of erroneous SI detection has a significant influence on the error performance of the system. And individual transmissions of SI result in the reduction of bandwidth efficiency. To restore the exact data signal, our scheme codes the SI bits by linear block codes (LBC), and is easily decoded by syndrome decoding. And then the coding SI bits are superimposed onto the logging signals to omit SI bits transmission. The theory and simulation results show that the proposed method has better performance than the conventional one. Accordingly, the OFDM wireless downhole transmission systems can tackle the high PAPR problem, and highten the transmission rate of logging signals.

Advanced Data Communications for Downhole Data Logging and Control Applications in the Oil Industry

We present details of 'Mercury', a high-speed downhole communications system that utilizes the (metallic) wall of a gas or oil pipeline or a drill 'string' as the communications 'channel' to control or monitor equipment or sensors used in the oil industry. Conventional downhole communication systems typically use 'mud pulse' telemetry for 'Measurement While Drilling' (MWD) operations. Current mud pulse telemetry technology offers bandwidths of up to 40 bit/s. However the data rate drops with increasing length of the wellbore and is typically as low as 1.5 bit/s – 3.0 bit/s at a depth of 35,000 ft. – 40,000 ft. The system described, by contrast, offers data rates of several megabits per second over distances of many kilometres and uses Orthogonal Frequency Division Multiplexing (OFDM) coupled with Wideband Frequency Division Multiple Access (W-CDMA). This paper presents details of our system; results of several trials undertaken on actual gas pipelines in the UK will be presented at the Conference.

The differences in the detectability of perforation shots and microseismic events in the surface monitoring: the attenuation effect

Detection of the seismic signal from perforations or string shots is crucial for calibration of velocity model for surface or downhole monitoring. While in the borehole recordings perforation shots have higher signal to noise ratio of the P-waves than microseismic events, in the surface monitoring recordings it is often opposite. We investigated amplitude spectra of microseismic events and perforation shots in the downhole data and found that amplitude ratios in the band of 20-30 Hz relative to band 100-200 Hz are stronger for the microseismic events. Thus we suggest that detectability of the perforations in surface recorded data is limited by attenuation of the higher frequency signal which increases exponentially with frequency. This suggests that longer duration of calibration shots can improve detectability of string shots at the surface. ARTICLE INFO

Engineering Aspects in the Design and Implementation of Onshore Smart Oil Fields

Summary The smart-field concept is deployed through disseminating elements of toolsand infrastructure integrated to bring a level of smartness that can improvethe performance of an oilfield asset in a sustainable way. The design andimplementation of these tools and infrastructure's underpinning smartness candiffer on the basis of oilfield conditions. Greenfields, for example, can beengineered upfront to leverage all tools and deliver smart-field value from thebeginning of the asset's life. On the other hand, smart-field tools andinfrastructure for brownfields would be designed selectively and be implementedon the basis of several engineering and economic considerations. The main functionalities of onshore smart field are remote operation,real-time information, and collaboration realized by the following tools andinfrastructure: Subsurface permanent downhole gauges (PDHGs) Subsurface flow controls Wellhead instrumentation Telecommunications infrastructure Supervisory control and data acquisition (SCADA) and control system Field-to-headquarters (HQ) connectivity Collaboration work environment (CWE) This paper outlines the engineering aspects to be considered in theselection, design, and implementation of tools and infrastructure for onshoresmart fields.

Seismic While Drilling (SWD) with a Rotary Percussive Sounding System (RPSS)

Seismic while drilling (SWD) with a rotary percussive drill used as the seismic source is presented. In addition to saving time by collecting seismic data while drilling, SWD also has the advantage of collecting a high data density with no additional effort and has a signal with a broad frequency spectrum. The only disadvantage is its signal-to-noise ratio is lower than many other seismic sources, although the signal-to-noise ratio is quite sufficient. The discussed methodology includes the triggering system and the stacking approach used to improve the signal-to-noise ratio. An example of SWD data is presented and compared to traditional down-hole (check-shot) data. Other examples of SWD are presented to demonstrate some of the data acquisition possibilities.

Petrophysical characterization of the lacustrine sediment succession drilled in Lake El'gygytgyn, Far East Russian Arctic

Abstract. Seismic profiles of Far East Russian Lake El'gygytgyn, formed by a meteorite impact some 3.6 million years ago, show a stratified sediment succession that can be separated into subunits Ia and Ib at approximately 167 m below lake floor (=~3.17 Ma). The upper (Ia) is well-stratified, while the lower is acoustically more massive and discontinuous. The sediments are intercalated with frequent mass movement deposits mainly in the proximal areas, while the distal region is almost free of such deposits at least in the upper part. In spring 2009, a long core drilled in the lake center within the framework of the International Continental Scientific Drilling Program (ICDP) penetrated the entire lacustrine sediment succession down to ~320 m below lake floor and about 200 m farther into the meteorite-impact-related bedrock. Downhole logging data down to 390 m below lake floor show that the bedrock and the lacustrine part differ significantly in their petrophysical characteristics. The contact between the bedrock and the lacustrine sediments is not abrupt, but rather transitional with a variable mixture of impact-altered bedrock clasts in a lacustrine matrix. Physical and chemical proxies measured on the cores can be used to divide the lacustrine part into five different statistical clusters. These can be plotted in a redox-condition vs. input-type diagram, with total organic carbon content and magnetic susceptibility values indicating anoxic or oxic conditions and with the Si / Ti ratio representing more clastic or more biogenic input. Plotting the clusters in this diagram allows identifying clusters that represent glacial phases (cluster I), super interglacials (cluster II), and interglacial phases (clusters III and IV).

“Imaging” the cross section of oceanic lithosphere: The development and future of electrical microresistivity logging through scientific ocean drilling

Abstract A detailed understanding of the architecture of volcanic and magmatic lithologies present within the oceanic lithosphere is essential to advance our knowledge of the geodynamics of spreading ridges and subduction zones. Undertaking sub-meter scale observations of oceanic lithosphere is challenging, primarily because of the difficulty in direct continuous sampling (e.g., by scientific ocean drilling) and the limited resolution of the majority of geophysical remote sensing methods. Downhole logging data from drillholes through basement formations, when integrated with recovered core and geophysical remote sensing data, can provide new insights into crustal accretion processes, lithosphere hydrogeology and associated alteration processes, and variations in the physical properties of the oceanic lithosphere over time. Here, we introduce an alternative approach to determine the formation architecture and lithofacies of the oceanic sub-basement by using logging data, particularly utilizing downhole microresistivity imagery (e.g. Formation MicroScanner (FMS) imagery), which has the potential to become a key tool in deciphering the high-resolution internal architecture of the intact upper ocean crust. A novel ocean crust lithostratigraphy model based on meticulously deciphered lava morphology determined by in situ FMS electrofacies analysis of holes drilled during Ocean Drilling Program legs (1) advances our understanding of ocean crust formation and accretionary processes over both time and space; and (2) allows the linking of local igneous histories deciphered from the drillholes to the regional magmatic and tectonic histories. Furthermore, microresistivity imagery can potentially allow the investigation of (i) magmatic lithology and architecture in the lower ocean crust and upper mantle; and, (ii) void space abundances in crustal material and the determination of complex lithology-dependent void geometries.

Modelling of temperature conditions near the bottom of well IDDP-1 in Krafla, Northeast Iceland

The transient temperature conditions near the bottom of well IDDP-1 in Krafla, which was drilled into a magma intrusion, have been simulated by some simple models of: (i) evolution of temperature conditions at the magma intrusion, (ii) cooling of the producing zone, a permeable layer above the intrusion, due to circulation losses during drilling and subsequent injection, (iii) reheating of the permeable layer after drilling and (iv) temperature evolution during the early phases of discharge testing in 2010. The modelling is not definitive, and does not consider later, more long-term flow testing (2011–2012), because the necessary down-hole data are lacking. However, results indicate that the evolution of the temperature conditions can be explained by these models. If the magma was emplaced during the most recent Krafla volcanic episode 25–35 years ago, the intrusion must have a thickness of at least 50–100m. The effective thickness of the permeable layer is estimated to be about 45m and its equilibrium temperature to be 390–400°C. No direct contact of the fluid with the magma is needed to explain the superheated steam discharged by the well. The situation near the bottom of the well clearly warrants further study, both through more advanced modelling and input of further data. The IDDP-1 well had to be quenched in July 2012. Whether it can maintain in the long-term the high energy output (15–40MWe), achieved during discharge testing, depends on sufficient recharge and efficient heat-exchange, if it can be rehabilitated. Carefully executed reinjection may be the solution if long-term recharge is not sufficient.

Technology Focus: Wellbore Tubulars (June 2013)

Technology Focus When the first pipelines moved crude from wellhead to market in the early 1870s, it was difficult to balance the product in the line to the storage tanks at each end. If the receiving station was not ready for the crude, the sending station risked pumping too much product and might have overfilled the receiving station’s tanks. Communications were by telegraph in those days, but telegraph lines were usually run along railroads, not pipelines. Instead of telegraphing what was coming down the pipe so that the receiving station could get ready for the volume, the sending station would open and close a valve and pressures and volumes would be received at the other end. Morse code by pressure waves was used instead of the electrical current and electromagnetism of the Cooke and Wheatstone telegraph. This pulsing is thought to be the beginning of the measurement-while-drilling mud-pulse technology of today. Several technological efficiencies have been achieved to increase the data rate of the mud-pulse technology, but they increased the data rate only marginally. Restricting the flow of mud inside the drillpipe through a poppet-and-orifice combination or modulating it through a siren would give longs and shorts like the dashes and dots of Morse code. Negative pulse technology added a small increase in efficiency. It used sharp pressure drops out the drillstring that provided a sharper signature at surface that was tied to time events and a few more bits could be compacted together. Electromagnetic systems send information to the surface with low-frequency electro-magnetic waves. The technology uses the flow of electricity to transmit bits. It has its applications but is dependent on the formation resistivity and depth. Wired drillpipe is a step-change solution for higher downhole data rates. If the cost can become competitive and the product is robust enough, data rates required to send high-definition images will be realized and the choice will exist to increase the data rate to 1 million times that of electromagnetic or mud-pulse telemetry. Tubulars are evolving to become data transmitters of increasingly larger band-width. In both the drilling and completion phases, greater bandwidth is required to monitor the stimulation of a well and to drill a wellbore more efficiently. Evaluating position in the lateral while drilling, monitoring drilling efficiencies downhole, and monitoring stimulation efficiencies all require greater bandwidth. Conventional wire and even fiber-optic cable are being used in innovative ways, in harsh conditions, to solve these evaluation issues. Recommended additional reading at OnePetro: www.onepetro.org. SPE/IADC 163420 Drillstring-Mechanics Model for Surveillance, Root-Cause Analysis, and Mitigation of Torsional and Axial Vibrations by Deniz Ertas, ExxonMobil, et al. SPE/IADC 163449 RFID—A Key Enabler in Drilling Automation by Mads Grinrod, Minerals Group, et al. SPE 157388 New Test for Material Resistance Against Microbiologically Influenced Corrosion by Jeppe Jensen, DTI Oil & Gas, et al.

Groundwater Visualisation System (GVS): A software framework for integrated display and interrogation of conceptual hydrogeological models, data and time-series animation

Summary Management of groundwater systems requires realistic conceptual hydrogeological models as a framework for numerical simulation modelling, but also for system understanding and communicating this to stakeholders and the broader community. To help overcome these challenges we developed GVS (Groundwater Visualisation System), a stand-alone desktop software package that uses interactive 3D visualisation and animation techniques. The goal was a user-friendly groundwater management tool that could support a range of existing real-world and pre-processed data, both surface and subsurface, including geology and various types of temporal hydrological information. GVS allows these data to be integrated into a single conceptual hydrogeological model. In addition, 3D geological models produced externally using other software packages, can readily be imported into GVS models, as can outputs of simulations (e.g. piezometric surfaces) produced by software such as MODFLOW or FEFLOW. Boreholes can be integrated, showing any down-hole data and properties, including screen information, intersected geology, water level data and water chemistry. Animation is used to display spatial and temporal changes, with time-series data such as rainfall, standing water levels and electrical conductivity, displaying dynamic processes. Time and space variations can be presented using a range of contouring and colour mapping techniques, in addition to interactive plots of time-series parameters. Other types of data, for example, demographics and cultural information, can also be readily incorporated. The GVS software can execute on a standard Windows or Linux-based PC with a minimum of 2 GB RAM, and the model output is easy and inexpensive to distribute, by download or via USB/DVD/CD. Example models are described here for three groundwater systems in Queensland, northeastern Australia: two unconfined alluvial groundwater systems with intensive irrigation, the Lockyer Valley and the upper Condamine Valley, and the Surat Basin, a large sedimentary basin of confined artesian aquifers. This latter example required more detail in the hydrostratigraphy, correlation of formations with drillholes and visualisation of simulation piezometric surfaces. Both alluvial system GVS models were developed during drought conditions to support government strategies to implement groundwater management. The Surat Basin model was industry sponsored research, for coal seam gas groundwater management and community information and consultation. The “virtual” groundwater systems in these 3D GVS models can be interactively interrogated by standard functions, plus production of 2D cross-sections, data selection from the 3D scene, rear end database and plot displays. A unique feature is that GVS allows investigation of time-series data across different display modes, both 2D and 3D. GVS has been used successfully as a tool to enhance community/stakeholder understanding and knowledge of groundwater systems and is of value for training and educational purposes. Projects completed confirm that GVS provides a powerful support to management and decision making, and as a tool for interpretation of groundwater system hydrological processes. A highly effective visualisation output is the production of short videos (e.g. 2–5 min) based on sequences of camera ‘fly-throughs’ and screen images. Further work involves developing support for multi-screen displays and touch-screen technologies, distributed rendering, gestural interaction systems. To highlight the visualisation and animation capability of the GVS software, links to related multimedia hosted online sites are included in the references.

Technology Focus: Drilling Technology (February 2013)

Technology Focus When searching OnePetro (www.onepetro.org) for papers dealing with “real time,” “drilling,” and “optimization,” one notices that 85% of SPE papers dealing with these three terms have been written over the last decade (2002–12). Indeed, there is an accelerated trend strongly supported by drilling companies (especially operators and service companies) of reducing nonproductive time, speeding up the learning curve, and optimizing drilling efficiency to reduce drilling cost and avoid unexpected failures. If drilling optimization is not new and dates back mainly to the 1960s, drilling-optimization departments and engineers today have an increasing number of tools (software and hardware) to facilitate their optimization tasks. Moreover, this can be achieved with a limited amount of investment compared with the huge cost reduction that can be gained. Depending on each application and purpose, many levels of drilling optimization in real time or almost real time can be achieved. From surface drilling data alone, mechanical-specific-energy surveillance can already be monitored to optimize rate of penetration, better detect the moment to pull the bit, and detect bit balling or vibration. Many companies have set up this process and have obtained very good results in drilling efficiency. Simultaneously having surface and downhole data (measured close to the bit or distributed along the drillstring) enables better assessment of the amount of energy transferred downhole (from friction loss along the drillstring) and enables better detection of downhole conditions (e.g., vibrations and hole cleaning). Predictive physical models coupled with surface and downhole data enable the addition of even more value because one can better detect ongoing or future abnormal conditions. For example, visualizing predictive critical rotation speeds (taken from dynamic modal analysis software), current rotation speed, and downhole vibration indicators on the same plot helps drillers adjust the rotation speed accordingly to avoid harmonic vibrations. Torque-and-drag and hydraulics calculation software is also very useful to detect deteriorating hole-cleaning conditions. However, if the tools exist to acquire, process, and visualize the drilling data, the most difficult part consists of understanding and interpreting the data to make a decision and provide the driller with a solution to mitigate the problem or optimize the drilling efficiency. This part is a real challenge because managing and analyzing downhole drilling data require highly skilled experts and analysts, to take full advantage of this information. Some of the papers selected for this month’s feature are good illustrations of the latest developments and applications in real-time drilling optimization. Recommended additional reading at OnePetro: www.onepetro.org. SPE 151176 The Effect of Equivalent-Diameter Definitions on Frictional-Pressure-Loss Estimation in an Annulus With Pipe Rotation by Olatunbosun Anifowoshe, University of Oklahoma, et al. SPE/IADC 151389 Drilling Performance Is a Function of Power at the Bit and Drilling Efficiency by Rolf Pessier, Baker Hughes, et al. SPE/IADC 151248 Directional-Drilling Tests in Concrete Blocks Yield Precise Measurements of Borehole Position and Quality by Ed Stockhausen, Chevron, et al. SPE/IADC 156445 BHA Modeling Coupled With High-Frequency Downhole Vibration Data Provides Unique Solution to Inconsistent Drilling Performance in South Iraq Oil Field by Paul Teasdale, Alwaha Petroleum, et al.

A Thermally Actuated Gas-Lift Safety Valve

Summary Most offshore oil wells use flow-control safety valves that are either actively controlled from the surface or passively actuated by pressure changes. In this paper, we propose a passive, thermally-actuated safety valve that adds redundancy to well systems and significantly increases well safety. We use quasistatic thermal modeling, validated with experimental downhole data, to identify and characterize a suitable temperature regime for shape memory alloy actuation. We develop a complete loading and shut-in procedure with the new valve that is consistent with current practice in artificial lift. Finally, through a true-scale stainless-steel prototype, we demonstrate essential manufacturability and successful valve closure in accordance with predictions.