本文主要介紹了石油上游行業在2008年開發出的新技術，其中包括信息收集、處理和模擬、軟件和測井技術。
New technology continues to amaze
With capital at their disposal, operators and service companies pulled out all the stops in 2008.
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TerraSpark’s Insight Earth provides advanced interpretation and visualization capabilities. (Image courtesy of TerraSpark)
Fueled by several years of high commodity prices, technology companies responded with some truly innovative developments in exploration technology. From acquisition to interpretation software, from electromagnetics (EM) to logging, every form of technology that aids in the search for oil and gas has seen improvements in 2008.
Acquisition
One of the most intriguing stories in acquisition is the Advanced Energy Consortium’s request for proposals to develop micro- and nanoscale technology for enhanced reservoir characterization and hydrocarbon detection. The AEC, a research consortium managed by the Bureau of Economic Geology at The University of Texas at Austin’s Jackson School of Geosciences, expects to fund US $6 million to $7 million in grants this year on micro- and nanosensor research and enabling technologies. The AEC received an overwhelming response to its inaugural request for proposals.
A wide variety of preproposals was received, and a “taxonomy” of the topics was developed to explain the portfolio (Figure 1). Sensor proposals fell into two categories, electric and nonelectric; electric sensors included proposals for microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS), and nonelectric sensors proposed constructing useful devices by exploiting the unique properties of a variety of nanoscale chemistries. As expected, a number of proposals were aimed at building up fundamental understanding of how nanoscale particles will move in complex fluids through semiporous oil and gas reservoir rocks (using models, simulation programs, and experimental designs).
In land seismic acquisition, CGGVeritas has introduced V1, combining high-productivity vibroseis acquisition technology with single vibrator operations. Benefits include point-source data for high-resolution imaging; high-density wide-azimuth data for better illumination, improved ground roll and multiple attenuation, fracture characterization, and reservoir characterization; and better performance.
ION conducted the first multiclient survey with its cableless FireFly land acquisition system, and AscendGeo’s Ultra G5 Cable-Free system was showcased in live real-time demonstrations of full-cycle seismic acquisition operations. The event demonstrated the advantages of cable-free shooting, including the operational efficiencies reported in recent projects in challenging environments. The product has been beneficial as a means of expanding traditional cabled systems in areas with environmental, urban, or cost challenges.
In the marine environment, WesternGeco is further developing new acquisition strategies. Coil shooting single-vessel full-azimuth (FAZ) acquisition ? a technique of acquiring marine seismic data while following a circular path ? takes geophysics further by improving on current multi- and wide-azimuth (MAZ and WAZ) techniques.
Typically, WAZ surveys are conducted using three or four vessels, each traveling in parallel lines. However, while conducting a project in the Gulf of Mexico (GoM), WesternGeco recognized that high-quality full-azimuth recordings could be achieved by acquiring data with a single vessel traveling in a circle.
In December 2007, the coil shooting method was tested in the Black Sea to image potential reservoirs related to carbonate reefs. The FAZ data delivered by the coil shooting technique provided better imaging relative to a previous conventional narrow-azimuth 3-D survey. In July 2008, WesternGeco was awarded the first commercial FAZ towed streamer survey using coil shooting in Indonesia.
PGS has introduced GeoStreamer, a new type of marine streamer that uses dual sensors to record a broader band of frequencies than conventional streamers. In addition to hydrophones, the GeoStreamer also has particle motion sensors similar to the geophones used in land seismic. While particle motion sensors are common in ocean-bottom cables (OBC), until now it’s been difficult to use them in marine streamers because the noise of being towed through the water masks the signal.
“You get all this noise from the tugging and the movement of the cable, which totally drowns out all these small signals you get through the particle motion,” said John Greenway, senior vice president of Marine Contract for PGS. “Different people throughout the years have tried to produce these things, but they’ve not succeeded. But now it seems we have one that works.”
The primary benefit of the streamer is that it can be towed deeper in the water, meaning less wave noise, and it provides a wide-broadband signal, recording both more lower and higher frequencies than conventional streamers. Deeper towing also means greater efficiency since the streamers can operate in choppy seas.
Another breakthrough is the first system to combine seismic and EM capabilities in an OBC system. Invented by MultiField Geophysics, the technology has been developed through a two-year joint research and development program with industry partners Wavefield Inseis ASA, StatoilHydro, and the Norwegian Geotechnical Institute.
The field tests involved deploying a series of seabed sensor segments to acquire EM and seismic data. The proprietary EM source, towing a horizontal electric dipole, was used to transmit various GPS synchronized arbitrary waveforms. Data were acquired and compared with a reference station deployed to monitor the spread and acoustic data collected simultaneously on selected acquisition lines.
Processing showed successful delineation of the gas field, and an analysis of the test data has confirmed the performance of the integrated EM and seismic system. Full-scale commercial operation is expected in Q1 2009.
Pure EM companies are also getting in the game. The idea of using EM techniques to measure subsurface resistivity to verify the presence of hydrocarbons has been around for almost 10 years. But up until a few years ago, the technique usually entailed a few 2-D lines acquired to confirm the presence of hydrocarbons in a target identified on seismic.
Over the last few years the emphasis has shifted to wide-azimuth 3-D. EMGS offers three 3-D EM products. The traditional prospect validation product (Clearplay TEST) has been joined by Clearplay FIND, which uses sparse 3-D grids to scan frontier areas, and Clearplay EVALUATE, which uses denser grids to deliver more detailed reservoir information for appraisal and development planning.
In August 2008, EM guided several successful bids in the Western GoM Lease Sale 207. The resolution of Clearplay EVALUATE enabled success even in cases where salt bodies would have rendered 2-D EM products useless.
In the world of remote sensing, advances in digital technology have since multiplied the value and variety of uses for imagery throughout the oilfield lifespan. DigitalGlobe recently launched Image Connect: Oil and Gas, an online imagery service for oil and gas professionals worldwide with on-demand access via GIS and WMS services to areas of global oil and gas exploration. This service offers high-precision, accurate views of geographic areas important to upstream oil and gas exploration, including oil basins, refineries, pipelines, and high-interest geological areas.
Processing and simulation
Data processors are always pushing the limits of even the fastest computers, and increasingly companies are turning to graphics processing units (GPUs) to aid in their computations. SeismicCity, a depth-imaging technology provider, recently turned to NVIDIA’s CUDA when processors discovered that each algorithm upgrade created a tenfold increase in computational intensity. Using CUDA on NVIDIA’s Tesla S870 1U server system provided a 20-time performance increase.
Schlumberger and WesternGeco, meanwhile, announced the purchase of Staag Imaging LP, a Houston-based provider of depth imaging technologies. The company is one of the first providers of a commercial full waveform inversion (FWI) technique, long the holy grail of data processors. Staag’s FWI is an automatic, data-driven tool that uses the two-way wave equation method to build highly accurate velocity models of the subsurface, including complex geological formations such as salt bodies. The technology can automate a large part of the velocity model-building workflow. These models are then used by WesternGeco for performing reverse time migration.
GeoMechanics International Inc. (GMI) launched a new service that provides 3-D mechanical simulations of the stress field around salt structures. This new service avoids unrealistic assumptions that are generally used for wellbore stability analyses, such as the concept that vertical stress is a principal stress, and thus is capable of providing a far more reliable prediction of safe mud weights than a standard analysis. Recent application of this service in exploration wells in the GoM showed that the prediction of the fracture gradient was significantly improved and the salt exit location could be optimized from a stability aspect.
PGS is using a process called beam migration to reduce the amount of time it takes to do prestack depth migration. Greenway explained that beam migration is a type of depth migration where the iterations required compute very quickly, leading to a final velocity model much faster than standard prestack depth migration.
“It saves a lot of time, energy, and cost in getting where you want to go and getting the velocity models right before you do the migration,” he said. “It is particularly effective in complex salt areas, and the models can also be used to run other migration schemes afterwards.”
Software
Where to start? Software innovations seemed to be almost a weekly event in 2008. Here are some of the highlights.
Recent start-up TerraSpark Geosciences LP launched Insight Earth, the company’s latest suite of interpretation software. Insight Earth leverages TerraSpark’s integrated technologies ? automated fault extraction, surface wrapping, and domain transformation ? to significantly improve geoscientists’ seismic interpretation results.
Ingrain, a Houston-based rock physics company, purchased a NanoXCT imaging device. The significance of Ingrain’s new imaging technology is that it can reveal unprecedented, nano-scale three-dimensional resolution of reservoir rock’s pore structures. Enhanced knowledge of these pore structures helps geoscientists determine how to best extract fluids from particular oil and gas formations.
Tierra Geophysical is a start-up company in Denver that specializes in software products that help geoscientists model their seismic surveys to be sure that the information gleaned from the survey will justify the cost. This is something that the industry has long realized could be a significant risk reducer. The problem is that it’s been too expensive to be practical for most surveys.
That is changing. “With more realistic modeling, it’s accurate enough that it can reliably address key risk issues about a lot of large decisions,” said Christof Stork, founder and senior scientist at Tierra. “Once you get to the point of considering a seismic survey, you know the geology you’re looking for. This technique is almost the classical scientific process, which we’ve never performed before in geophysics. You make a hypothesis, and then you test it.”
Another software development that’s just getting underway is happening at FFA. The company has been focusing on volume processing and 3-D seismic computing attributes, deriving geobodies by imaging faults and structural elements. Recently it has teamed with Hewlett-Packard and NVIDIA to take advantage of the new compute power available to the industry through NVIDIA’s ability to use GPUs to process seismic data.
“The computer power available to the industry has taken a step forward,” said Stephen Purves, technical director for FFA. “When we’re computing on a workstation with NVIDIA graphics, we can do a lot more processing on the desktop.”
Their plans are to take the volume processing engine and technique and parallelize it with the new technology, which will allow rapid seismic data analysis.
At Paradigm two new products hit the market this year ? Common Reflection Amplitude Migration (CRAM) and Subsurface Knowledge Unified Approach (SKUA). CRAM provides a ray-based solution that maintains all of the flexibility of the Kirchhoff migration while inheriting the desirable properties of full-wave migrations. This prestack depth migration seeks a uniform illumination of the subsurface by performing a dense ray tracing from every image point up to the surface. These rays are traced in uniform angle increments and in all directions to ensure that all arrivals are taken into account and all amplitudes and phases are persevered.
SKUA brings a new perspective to gridding. It unifies all subsurface discrete models by embedding a native, fully 3-D description of the faulted volumes. Horizon and grid geometries are constructed simultaneously in 3-D space. This is achieved by using a technology based on the observation that horizons represent geochronologic surfaces.
Logging
Production logging is often used to determine where oil and gas are entering the well bore, but rarely has this information been present during the initial logging run after a well has been drilled. Apache Corp. and Weatherford International have plans to change that scenario.
Werner Heigl, senior geophysicist for Apache, has developed a process for using sonic log data to analyze the velocity of the drilling mud inside the well bore. “Water has certain velocities for waves to propagate through,” Heigl said. “When the water has gas dissolved in it, the velocity of propagation drops drastically.” He added that a 1 to 2% volume of gas could result in as much as a 10 to 20% drop in velocity.
So far Apache has experimented on 10 wells with generally very good success. It has patented the process and will license it through Weatherford. One of the main advantages, Heigl said, is in designing completions for tight-gas wells.
“In tight rocks, a standard petrophysical analysis has a lot of uncertainty,” he said. “Operators tend to over-complete because they don’t want to miss anything. With this new method, you can actually see which zones are contributing, so they can reduce the number of intervals to perforate and optimize the completion while getting the same production.”
Other companies are also looking at existing well log data to find new answers. Seismic Micro-Technology, for example, has added neural log replacement networking to its KINGDOM interpretation software. The neural network technology can fill in missing information from older, incomplete logs, analyzing all known information about that particular part of the subsurface from the rest of the log and other similar logs to reconstruct the lost data. The solution is also self-training, unlike other neural network technology.
The drop in commodity prices could result in less research and development spend going forward. But creativity has a way of surviving downturns. Expect 2009 to bring even more surprises.
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