Borehole Seismic Services
Wireline borehole seismic services are an essential and growing part of reservoir evaluation, especially for horizontal drilling and hydraulic fracturing. Of all the wireline services, borehole seismic delivers an industry-leading depth of investigation abilities and links the borehole-to-surface seismic measurements that span basins.
Weatherford microseismic, hydraulic-fracture mapping service brings together world-class seismologists, field operators, and state-of-the-art seismic tools to record, process, and interpret microseismicity from single-staged or multi-staged hydraulic-fracture stimulations. This service provides 3D renderings and animations of fracture-network initiation, growth, and in-filling.
A Brief History of Microseismic Mapping in Unconventional Reservoirs
Microseismic monitoring has played a critical role in the success of oil and gas production from unconventional reservoirs over the last ten years. Several surveys spanning that period, including the first survey in a shale gas field, describe the evolution of that success. These case histories illustrate important lessons learned about influence of fine geologic structures on the fracture behaviour of these reservoirs during stimulation. These stimulation mapping examples chronicle the evolution of modern completion techniques to address and exploit these reservoir complexities. They describe the economic impact of applying microseismic monitoring to these operations.
Distributed Acoustic Sensing - A New Way of Listening to Your Well/Reservoir
Kjetil Johannessen, Statoil ASA; Brian Keith Drakeley, Weatherford; Mahmoud Farhadiroushan, Silixa Ltd
A new generation of in-well monitoring technologies is being characterized under the Acoustic Energy sensing banner. Some are essentially disturbance or vibration event monitoring techniques, but this paper describes a Distributed Acoustic Sensing (DAS) technology . The subject sensing system uniquely allows the user to listen to the acoustic field at every point along many kilometers of fiber optic cable deployed in the well. With a spatial resolution of 1 meter, for example, there will be 10,000 synchronized sensors along a 10,000-meter fiber. The system uses a novel digital optical detection technique to precisely capture the true full acoustic field (amplitude, frequency, and phase over a wide dynamic range) at every point simultaneously. A number of signal processing techniques have been developed to process a large array of acoustic signals to quantify the coherent temporal and spatial characteristics of the acoustic waves. Potential in-well monitoring applications have been identified, and significant benefits are predicted for optimizing and maximizing production in many types of oil and gas fields by facilitating informed decisions. The system can be retrofitted to existing installations of permanent in-well fiber optics-based monitoring systems with the addition of surface instrumentation. New installations are also planned. This paper also describes the background technology with focus on full reconstruction of the acoustic signal along the well bore, sensing system capabilities, and the results of field trial surveys with first-generation instrumentation in seven offshore Norwegian Continental Shelf wells that already contained in-well fiber optics sensing systems. An acoustic signal for flowing wells was obtained in all cases. For most of the wells it was also possible to extract qualitative information on the flow regime, speed of sound, and an estimate for flow velocity in at least parts of the wells.
Ten Years of Microseismic Mapping of Shale Gas Completions: Lessons Learned
Microseismic monitoring has played a critical role in the success of shale gas production in North America over the last ten years. Several surveys spanning that period, including the first survey in a shale gas field, describe the evolution of that success. These case histories illustrate important lessons learned about influence of fine geologic structures on the fracture behaviour of these reservoirs during stimulation. These stimulation mapping examples chronicle the evolution of modern completion techniques to address and exploit these reservoir complexities.
Flow-Induced Noise in Fiber-Optic 3C Seismic Sensors for Permanent Tubing-Conveyed Installations
S. Knudsen, G. B. Havsgård, A. Berg and T. Bostick
This paper reports the test results acquired of flow-induced noise in a fiber-optic 3-C seismic station, where the tests represent some of the possible conditions that may be expected in flowing wells. The tests were performed to evaluate a fiber-optic sensor tool for tubing-conveyed installations in a controlled-flow test facility. The results of these tests demonstrated that the active-coupled 3-C fiber-optic seismic station installed on production tubing inside cemented well casing was capable of detecting very small seismic signals at high single-phase flow rates for frequencies in the 10 to 600 Hz band. Test results also demonstrated that the active 3-C station has a very efficient decoupling from flow-induced noise (compared to a passive 3-C seismic station directly attached to the production tubing), while at the same time having good coupling to the casing and formation. Test results showed that two-phase flow increased the noise at high frequencies over that of single-phase flow; however, for frequencies <100 Hz the noise increase is small. This testing indicates the potential to acquire high-resolution, multi-component seismic data in flowing wells under certain conditions with fiber-optic sensors.
Time-lapse VSP Field Test For Gas Reservoir Monitoring Using Permanent Fiber Optic Seismic System
Jacques Blanco, Geomec Sverre Knudsen, and F.X. (Tad) Bostick III, Weatherford
In a gas storage reservoir, the seismic monitoring of the gas bubble expansion or contraction as a function of injection or withdrawal is very attractive for reservoir management. However, the accuracy with which small seismic changes have to be measured for the monitoring of a gas bubble in a shallow gas storage reservoir requires seismic surveys with an excellent degree of sensitivity, such as can be found in borehole seismic surveys. A promising borehole seismic technique for reservoir monitoring is the use of permanently installed seismic sensors in wellbores. Yet, the effectiveness of distributed permanent seismic sensors in well can be limited by signal contamination induced by the borehole and the well completion. Repeatability is recognized as one major issue for improving the time-lapse seismic approach. To maximize repeatability, several walkaway VSP surveys using a permanent in-well fiber optic seismic system were acquired at different cycles of gas injection and withdrawal. Different configurations were tested to reduce the amplitude of undesirable tube waves and to enhance the signal-to-noise ratio. Finally, the results show that time-lapse VSP might be an efficient tool for gas reservoir monitoring.
Three Different Methods of Mapping the Characteristics of Induced Fractures Related to Both Hydraulic Frac and Production as Measured With Microseismic Array Technology from Observation Wells, Treatment Wells and in Permanent Setting
Nicholas Brooks, Graham Gaston, Jaime Rangel, Weatherford
Passively listening to induced fracturing that is related to production or hydraulic stimulation from a downhole setting has become widely accepted in the oil and gas business. Completions planning and infill drilling programs continue to benefit from this technology with the ultimate goal of enhancing recovery whilst reducing overall costs. The mapped microseismic events are driven by localized and regional stress directions and pre-existing fracture networks. The microseismic map influences the subsequent interpreted fracture network. Reservoir performance and hydrocarbon recovery can be optimized by correctly applying the right downhole monitoring technology to a given specific objective. Here we present three different methods for collecting microseismic data from a downhole environment. We demonstrate the variable response of a single reservoir to hydraulic fracture treatment. Standard observation well setup and treatment well deployments are discussed and case histories are shown. We weigh the benefits and drawbacks of both. With the advanced observation well tool, we show better lateral coverage with high variability of formation response. The tool that can be deployed in the treatment well itself shows better accuracy of frac height measurements and highly localized changes in frac orientation but with limitation of lateral coverage. Extending the monitoring window to years or decades requires yet a different approach. The unique system that contains no downhole electronics extends the life expectancy of the monitoring array for true permanent applications. The three distinct techniques of observation well deployment, treatment well deployment, and permanent deployment are successfully applied and demonstrated with case studies. The data that is collected can be used for planning and optimization in the short, medium, and long term. When applied in difficult and unconventional settings, this leads to increased reservoir performance and reduced overall cost.
Microseismic Monitoring of Multistage Hydraulic Fracturing in Complex Reservoirs of the Volgo-Urals Region of Russia (Russian)
A. Konopelko and V. Sukovatyy, Gazprom neft Orenburg CJSC; A. Mitin and A. Rubtsova, Weatherford
One of the most frequently used and efficient flow enhancement methods is creation of a wide network of induced formation fractures and activation of filtration in natural fractures with the help of hydraulic fracturing. This technology is being actively used worldwide and on the whole territory of Russia. Geomechanical properties of a formation, its structure, and the direction of maximum horizontal stress play a critical role in application of the flow enhancement method with use of hydraulic fracturing. The majority of currently developed reservoirs have a complex, inhomogeneous structure; that is why adequate prediction of hydraulic fracturing outcome becomes a challenge. In addition, execution of such expensive and labor-consuming operations without painstaking planning and understanding of the final result, especially in case of massive hydraulic fracturing on the field, is practically impossible. To solve this task, a whole complex of solutions was developed, including microseismic monitoring—a passive seismic listening technique that enables mapping of the fracture network created during hydraulic fracturing, determining their principal orientation, and evaluating the reservoir geomechanical properties. Microseismic monitoring of hydraulic fracturing is one of the most reliable means to map the fracture network formed as a result of hydraulic fracturing. Fractures often feature a rather complex structure that does not allow for modeling the outcome of hydraulic fracturing with required precision based on reservoir geology and fluid dynamics model. This leads to low fracturing efficiency, significant time and costs. This paper provides results of microseismic monitoring of hydraulic fracturing performed on a well in the oilfield of the Volgo-Urals region of Russia in 2014. It demonstrates importance of comprehensive study of fracture space structure on the field for effective development. As a result of monitoring, the presence of two fractures systems different by directions were recognized. Several conclusions were made regarding possible reasons of that and about the necessity of further investigations of reservoir properties, which is built with rocks of different structure.
Simultaneous Recording of Hydraulic-Fracture-Induced Microseisms in the Treatment Well and in a Remote Well
Kenneth D. Mahrer, Weatherford; Richard Joseph Zinno, Precision Energy Services; Jeffrey R. Bailey, ExxonMobil Upstream Research Co.; Matthew M. DiPippo, ExxonMobil Production Co.
In June 2006, in a production well in a tight sandstone shale sequence, onshore USA, two borehole seismic arrays were deployed in separate wells during a proppant-baring hydraulic fracture treatment. The intent was to delineate the treatment-generated fracture network by recording the microseisms triggered by the treatment, mapping the microseism source locations, and then using the map as an overlay to delineate the fracture network. The treatment was one facet of a proprietary, multifaceted injection strategy with microseismic mapping used to determine if neighboring fracture networks overlap. In addition to mapping the network, the objective of this facet was to compare maps from the two arrays. One array was in a remote well and the other in the treatment well. The remote array was offset ~700 ft from the treatment well and at the injection depth. This array was ~500 ft long and self-locking, contained 15 three-component motion sensors, and operates on a fiber-optic cable. The array in the treatment well—the "TABS” or triaxial borehole seismic array (licensed by ExxonMobil Upstream Research)—is ~75 ft long and self-locking. It operates on a standard, 7-conductor wireline and includes three 3-component motion sensors, an ambient fluid pressure sensor, and a gyroscopic, sensor-orientation package. During the treatment, a 45-minute injection immediately followed by a 1-1/2-hour well shut-in, the remote array failed to detect any discernable treatment-triggered microseisms. However, TABS, which recorded microseismicity only during the shut-in, recorded ~400 microseisms. During the operation, the remote array maintained one position; TABS was unlocked, repositioned, and relocked twice. Moving TABS allowed different perspectives for recording the microseismicity, improving the accuracy of mapping and enhancing additional characteristics extractable from the microseismic waveforms.
Our borehole seismic service places multiple geophone sondes in an array configuration in the wellbore and clamps the sondes to the casing or open-hole surface.
The geophones record seismic activity generated by either artificial, impulsive-seismic sources, such as borehole-sparker sources and surface vibroseis buggies (active seismic recorders), or the naturally occurring seismicity, such as microearthquakes induced by fluid injection or fluid withdrawal from the reservoir (passive monitoring).
Weatherford has the capability to deploy multilevel seismic arrays and seismic sources in various configurations to fit each purpose.
- Monitoring hydraulic fracturing operations for real-time observation of the subsurface effects of surface pumping operations
- Mapping anomalous well drainage patterns due to natural fractures and faulting
- Evaluating stimulation program effectiveness
- Defining efficient well placement for infill development
- Correlating time-to-depth seismic surveys
- Correcting time of synthetic seismograms from sonic and density logs
- Correlating time-of-surface seismic surveys and well logs
- Full-wavelet extracting of surface seismic surveys
- Correcting target depths ahead of the bit during exploratory drilling
- Correcting interpreted geologic horizon picks
- High-resolution imaging of structure and sediments around and below the well
- Calibrating modeling software to quantify fluid saturations on surface-seismic volumes
- Calibrating modeling software to quantify and map-fracture densities on surface seismic volumes
Our innovative offerings include: The only purpose-built, borehole-microseismic arrays in the industry; the only in-treatment, well-microseismic monitoring; a microseismic spear array; and our Clarion system—the most robust and sensitive fiber-optic, permanent-seismic array.
Our modern, global vertical seismic profile (VSP) service is based on a core team of expert geophysicists, dedicated seismic-specialist engineers, and advanced, strategically deployed equipment. In local districts, we have placed easily transportable seismic-source kits, appropriate to the needs of our local clients.
The Weatherford frontline SlimWave™ microseismic array uses the revolutionary orthogonal frequency-division multiplexed (OFDM) telemetry, which delivers extremely broad bandwidth-information streams up most standard wirelines used in the oil industry.
This telemetry flexibility allows high sample rate recording in the most remote corners of the world. A single array can be transported by air from one survey in the mountains of Colombia to remote Siberia and perform perfectly and reliably on completely different cable systems. We can go most anywhere.
Collaboration between Weatherford and a Russian operator has helped develop a fit-for-purpose well plan in horizontal-development programs.
By incorporating the observations and recommendations from the Weatherford microseismic-monitoring service into the drilling and completions strategy, the operator’s anticipated oil production rates increased nearly 400 percent in the first 90 days. This success has led other operators to adopt the technology more broadly, which has resulted in better production from their horizontal development programs.
For more than 20 years, the our Clarion seismic-monitoring array has led the industry in permanent, passive-seismic monitoring and 4D VSP projects in production wells, both offshore and onshore.
Weatherford offers accurate, borehole seismic services on six continents featuring a wide variety of deployment options for improving the performance of conventional and unconventional reservoirs. We combine this with state-of-the-art professional seismic survey design and stimulation supervision through our partnership with the world-renowned consulting service, Ely & Associates. By combining our array of openhole-logging options, logging-while-drilling (LWD), and geomechanical analysis capabilities, we make a complete picture of the reservoir behavior available to our clients. This helps provide enhanced wells, with less waste and improved economics.
- Microseismic Hydraulic Fracture Mapping Service
- Well-Integrity Monitoring
- Vertical Seismic Profile (VSP)