Microseismic Monitoring

Passive Seismic Tomography

Exploration Geophysics

Welcome to the latest newsletter of Landtech-Geophysics Ltd.We are a UK-registered company that now exclusively incorporates LandTech SA – the inventors of high resolution Passive Seismic Tomography (PST) for hydrocarbon exploration.

All of LandTech SA’s engineers now form part of our powerful scientific capability incorporating an unrivaled number of years of experience in Passive Seismic surveying, Passive instrumentation, Passive Seismic data processing, oil & gas reservoir monitoring and Shale Fracking services. With this expansion and reorganization, Landtech-Geophysics Ltd. can now efficiently support many simultaneous geophysical surveys anywhere in the World without sacrificing the well recognized quality of its services. [Note we have no relationship with the company Seismotech].

The new company will continue to expand its PST services for the upstream Industry worldwide. Furthermore, we are developing new advanced tools to extract even more information from the PST data volumes below an exploration block such as: fluid content, detection of hydrocarbon traps, favourable drilling sites, overpressure assessment and other important characteristics.

How to use PST to reveal the hydrocarbon potential below an entire exploration block

Our innovative in-house seismometers are used for recording and analyzing the tiny cracks and groans of the earth (microearthquakes). From these, we can derive high resolution 3D seismic tomography images of compressional P-wave velocities, shear S-wave velocities, Poison's ratio seismic attenuation or quality factor Qp for the whole of an exploration block at a fraction of the cost of conventional seismic surveys. Difficult topography is not a problem.

Patented neural technology provides lithological information and proposes drill site locations with the highest probability for successful wells. An example of how a 3D PST data volume can be used is depicted in the following figure:

In this issue:

?Using PST to reveal the hydrocarbon potential below an entire exploration block

?We put the standards in automated passive seismic data processing

?Combined use of Gravity and PST data.

?Common FAQ about Pasive Seismic Tomography

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3D Passive Seismic Tomography used to provide drill locations for successful oil wells

continued from page 1... unsupervised artificial Kohonen neural networks Furthermore, the use of P and S waves is very helpful (Fig.3) and Self Organizing Maps (SOM) algorithm in in identifying fluid type in porous reservoir rocks. It is passive seismic data analysis proved to be a useful found that P-wave velocity decreases and S-wave tool for delineating the structural ad lithological velocity increases with the increase of light properties of the hydrocarbons in place of brine saturation. This is true subsurface. within the range of free gas or free hydrocarbon saturation. From observation, it is found that light We train a neural hydrocarbon saturation decreases the velocity of network by using compressional wave and increases the velocity of Vp, Vs, Poisson í shear wave through porous rocks (relative to and Q 3D data. formation water saturation). Either shear waves or An example from compressional waves are conjugated. The fact that a gas and an oil the compressional wave is affected by changes in field in SE size and deformation means replacement of water by Albania where gas will decrease density and also elasticity (change PASOM© in size, bulk modulus k and deformation, shear technique modulus ì; only deformation which is absorbed by pinpointed the gas). This causes a decrease in the compressional two producing wave. When gas saturation reaches residual gas zones is depicted saturation and the water becomes the major fluid, in Fig.2 (right).there is no gas free to absorb deformation so the shear wave velocity will suddenly increase. On the other side, the compressional wave velocity will not be much affected and it will maintain the same increasing trend with increases in water saturation. Although the analysis of S-wave data can significantly reduce the uncertainty in interpreting conventional seismic data, such data are much more difficult to collect.

Passive Seismic techniques can provide reliable VP and VS data below an entire block and at a fraction of the cost of conventional methods that only provide data locally. LandTech has recently developed a new revolutionary geostatistical methodology (PASOM©) based on Kohonen neural networks and PST data attributes to derive lithological information of a region where a PST survey has been conducted. These attributes are: Vp, Vs, Poisson í and the attenuation quality factor Q. The use of

(e.g. VSP)

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Figure 3: Using a neural network, structural and lithological information can be obtained

Figure 2: Application of PASOM method in Gas & Oil producing block

Landtech Geophysics In the News:-Feasibility study for reservoir microseismic monitoring and seismic fault mechanisms in Mexico. Client: PEMEX-Microseismic monitoring of the aftershock sequence of the 6.1 earthquake in (Greece) with tomographic inversion for seismic data. Client: Ministry of Public Works.-LandTech-Geophysics exhibited its services on passive seismic tomography and 84th SEG annual meeting at Denver USA. -LandTech-Geophysics moved to its operation to new offices at Cardiff, UK.-LandTech-Geophysics has developed a new highly sensitive 32 bit seismometer with signal compensation to be used forshale fracking monitoring.

Cephalonia

Installing our Lt32 seismic station in Mexico to record reservoir induced seismicity

Our shale fracking -3-axis sensor. Wide Bandwidth 4.5-500Hz.

Combined Use of PST and Gravity Data

If required, LandTech-Geophysics can offer combined interpretation of PST, Gravity and or

Magnetotellurics services.

In the figure below, we present the synthetic Bouguer Gravity map derived from PST data in an exploration block in SE Albania.

LandTech-Geophysics engineers have developed joint interpretation procedures utilizing various combinations of data obtained from different geophysical methodologies (e.g. passive seismic, magnetotellurics and gravity) and have applied them in geologically complicated regions. These include: thrust belts and regions of severe seismic penetration problems (e.g. basalt covers or salt dome mapping). In the plot below, using certain criteria (5.2km/s < Vp < 5.3km/s, 1.78 < Vp/Vs < 1.80, 2.65 g/cc < density < 2.665 g/cc, 2.5km < depth < 3.5km) a combined PST and gravity dataset for a gas field region has been delineated (ellipse) and confirmed by drilling.

Landtech-Geophysics sets the standards in automated Passive Seismic data processing

Vol.77, No6, Nov-Dec 2012.

A new automaticS-onset detection technique: Application in local earthquake data. Geophysics, Vol.78, No1, Jan-Feb 2013.

As the seismic stations recording in a PST Example of automatic picking of P– and survey increase in number and sampling S– phases in a noisy seismogram using frequency, datasets become too large for LandTech’s methodology.manual processing to be effective. Event detection and accurate arrival time picking And during the 84th SEG meeting at from the recorded seismograms can be Denver: An integrated processing tool for very hard due to the generally low signal- Microseismic data analysis.to-noise ratios (S/N) of the recorded events. (above) Example from the

A high resolution PST survey requires the processing of vast amounts of noisy data acquired over thousands of hours of 3-component continuous recording.. The algorithms have to recover the useful parts that correspond to the local microseismicity, and isolate the corresponding seismograms containing useful information which are sometimes invisible. This applies to

LandTech-Geophysics has made significant investments in developing advanced state of the art software to process PST data, putting emphasis on resolution and

implementation of the proposed quality control.

methodology on seismic data (upper plot), as well as P- and S- arrival times

In Passive Seismic Tomography estimation for the selected events in the

investigations, the accuracy of the arrival black rectangles (bottom plots).

time picking of P- and S- waves is essential to the final result. Although there

(below) An example of the are many automatic picking algorithms

implementation of the proposed mainly used by seismological institutes,

methodology on poor quality seismic they are not convenient for a high

data recorded in Delvina, Albania, during resolution PST survey due to the fact that

a hydraulic fracturing experiment. The we are interested in very small magnitude

3C seismic record with the detected microearthquakes (sometimes negative

segment (red dots), and the magnitudes) often embedded in the noise.

corresponding characteristic function in graph (d).

Our P- and S-wave arrival time detection algorithms are based on Higher Order Statistics (HOS) methods, skewness, kurtosis and differential entropy (also known as negentropy) and not on the simple STA/LTA (Short/Long Term Averages) methodologies used in classical seismology. Furthermore, advanced Winner and Kalman filtering data conditioning stages and neural networks are used during the various processing stages.

Some latest achievements of our engineers concerning these revolutionary seismic processing methodologies have been published in the Geophysics publications of SEG including:

-Strategy for automated analysis of passive microseismic data based on S-transform, Otsu’s thresholding, and higher order statistics. Geophysics,

all the stations of the passive network.

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Some common FAQ concerning PST

When the Earth Whispers we are there!

1. Is my region appropriate for Passive Seismic Surveys?Microseismicity occurs almost everywhere. LandTech-Geophysics instruments are specially designed to record microearthquakes down to –4R! In areas that show a small amounts of seismic activity, we conduct a feasibility study at cost price only prior to the beginning of a PST project.

2. What is the cost of a passive tomography investigation? The cost to perform a PST survey in an area is a fraction of the cost of a conventional seismic survey, and 3D data are also obtained. An indicative cost is $1.5M per 1000Km2, however cost is not proportional of the dimensions of the exploration block. For example, to investigate a block of 8000Km2 the cost can be as little as $3.5 M.

3. Are the data obtained less accurate than those of a conventional seismic reflection survey? In many cases the results are even better. For example, in regions with rough topography or complicated geology (e.g. thrust belts) results are much more accurate. In fact, in regions that encounter seismic energy penetration problems either because of heavy weathered surface layers or because of the existence of evaporitic formations, PST is the only technique which can provide excellent results.

4. Can we be sure about the accuracy of the PST results? PST results are very accurate. They have been crosschecked even with the results from VSP's and in some cases differ by less than 5%!. Furthermore, LandTech has a series of Quality Control Tests that use synthetic and inverse modeling to ensure the accuracy of the models we provide to our customers.

5. How long does it take to conduct a 3D passive seismic investigation? It depends on the background seismicity of the region. In general we can supply detailed 3D Vp,Vs and Poisson's ratio maps and 3D crustal property animations within 6 months. Prior to the main survey, Landtech-Geophysics performs a pre-feasibility research at no cost, considering the seismicity of the region and its geotectonic structure. This enables us to provide the client with an optimal number of passive stations and the timeframe for the project.

6. How long can a seismograph be operated in regions with no electricity? Our LTSR-32 bit digitizer has been designed with this question in mind. It is the lowest power consuming seismic recorder in the World since it writes directly from the A/D converter to a Flash or SIM card. It can operate for almost a month from a small 12v motorcycle battery. In addition to this, our engineers have developed various ways of keeping our seismographs running even in the most isolated regions using solar panels, micro wind generators and recently, the new technology of Hydrogen and Methanol cells.

7. Can I apply this methodology in areas of very rough topography? PST methodology is not affected by rough topography. Since we do not have to deploy many geophones or deploy seismic lines and repeaters, we do not have to use surface seismic sources. It is extremely easy to operate in rough terrain environments. All we have to do is to install single stations at a spacing of around 3-5KM, use GPS for accurate positioning and let nature to act as the seismic source. We have operated in thrust belts with topography ranging from a few metres to a few KM above sea level. If required, we use helicopters to deliver recording equipment to remote sites and reduce layout / data retrieval times, although this is not often required.

8. Can you operate offshore? Landtech completed the design and tests of a unique Ocean Bottom Seismograph that is able to operate up to depths of 10KM and synchronized via an atomic clock. This unit enables Landtech to carry out offshore passive seismic tomography surveys.

9. Can PST methodology differentiate oil and gas reservoirs? Landtech also provides Vp/Vs ratios below the entire block - a parameter that is especially sensitive to the pore fluid found in sedimentary rocks. Specifically, the Vp/Vs value is much lower (10-20%) for gas rather than liquid saturation making differentiation possible.

10. What are your guarantees. We have many high profile clients who are satisfied with the services of Landtech and letters of recommendation are available on request .

11. Can you pinpoint drilling sites?By putting certain constraints on the variation of the PST parameters such us expected reservoir depths, velocities that characterize the hydrocarbon bearing formations, expected Poison's ratios and using artificial neural networks, we can provide our clients with locations having the highest probabilities for successful wells.

www.landtechsa.com & www.landtech-geophysics.com

Registered UK office: Landtech Geophysics Ltd., Ty Menter, Navigation Park, Abercynon CF45 4SN, United Kingdom Tel: +44 (0)2921 660272

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