Services Provided directly by iESog

  • Wellsite and Operations Geology Supports (WOGS)(SOR & WLR, CFT, WPS, AUDIT, DGR, PVA, FWR / GEOWR)
  • Seismic Interpretation (SI)
  • Structuro-Sedimentary Analyses (SSA)
  • Pore Pressure Prediction (PPP)
  • Petroleum evaluation (PE)
  • Trap and Seal Analyses (TSA)
  • On-the-Job Geoscience Training (OGT)

ON-THE-JOB GEOSCIENCES TRAININGS covers the above services, where we work with in-house staff on the various services.  The personnel develops skills and is able to replace our services in due time.

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Services

  • WELLSITE AND OPERATIONS GEOLOGIST SUPPORTS

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    We supervise the mudlogging team, carry out the audit and ensure the various sensors measuring drilling parameters works efficiently. Alongside the LWD, mudlogging and drilling teams, we shall monitor drilling parameters and process, then collect and interpret downhole samples.

    In order of a well progression, we provide:

    • Statement of Requirement
    • Well Location Report (WLR)
    • Call For Tender (CFT)
    • Well Prognosis Sheet (WPS)
    • Audits
    • Daily Geological Report (DGR)
    • Prognosis Versus Actual (PVA) Results
    • Final Well Report (FWR)

    The WSG carries out an audit of these systems and the Mudlogging unit. Then prepares a report saying if everything is set up properly and functional.  The Wellsite geologist also give a Statement of Quality Management (SQM) report to the Operations Geologists or Head of Operations at the base. The WSG should also keep a Personnel On Board (POB) and equipment records in collaboration with the ML team. Validation of proper execution of contractual terms and payment to the service contractors is based on this. 

    It is the wellsite geologist’s duties to check:

    • That gas calibration is OK; the total gas equipment is calibrated with methane
    • the backup systems (e.g. real time monitors)
    • ensure that gas line is clean and dry
    • keep an eye on the density out to know the percentage gas in mud (mud weight before and after)

    The WSG geologist is supposed to have a triangular communication pattern between the ML units, the drillers and the company man. We supervise the Logging while drilling and provide on the fly and quick look Log Interpretation. After each well we prepare the  End of Well or Final Well Reports (FWR). A FWR will include:

    • Well general information
    • Drilled operation for each section
    • Geology and petroleum results
    • Pressure results verses prognoses
    • Acquisitions result (Petrophysical logs, Gas, Core)
    • Confirmed stratigraphies
    • Well testing or Abandonment

    The FWR remains the main reference document for a well post drilling.  In general, we provide:

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  • SEISMIC INTERPRETATION

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    Our seismic interpretation starts from the basics to highlights:

    • Eye observation and identification of geological features on the seismic from experience and deduction based on geological principles
    • Tracing out the reflectors on a 2D or 3D seismic image or block (on paper or on the workstation) and then tying them together to form a map
    • Analyzing the empirical values from seismic data, example speed or amplitude values and applying them to causal factors.

    One basic step in seismic interpretation is the elimination of artifacts, which are observations that are not real but introduced by errors.  Among other things to be isolated before interpretation, or at least identified, are multiple reflections and tuning effects resulting from interferences of signals.  Seismic images are interpreted by our geophysicist, geologist and engineers – it requires a collaborative work to make the most of it.  It is possible to extract amplitudes, cut seismic blocks to vertical or horizontal slices, play them as movies using specific software.  Eventually migration pathways, amount of reserves and many other pieces of useful information of a petroleum system, including volumetrics of hydrocarbon, are derived during seismic interpretation.

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  • STRUCTURAL AND SEDIMENTARY ANALYSES

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    Following detailed comparison between maps and seismic sectures, we provide a report of the interrelationship between geologic structures (such as faults, folds…) and sedimentary profile (process, deposition types and lithology). In existing petroleum fields, this is collaborated with well data. Data from nearby well are correlated to the area of interest and used to predict subsurface conditions.

      

    Evaluation of sedimentary profile will cover:

    • The sedimentation process
    • Depositional types and environment
    • How basins are formed
    • Petroleum Basin analyses
    • Basin temperature
    • Basin pressure
    • Evaluation of Structural features will cover
    • Deformation – folding
    • Plate movements
    • Formation of basinal structures
    • Structural restoration and decompaction
    • Integrated Basin Modeling 
    • Relationship bettween burial, temperature and pressure

    The above forms the bases for a petroleum basin analysis, during which we ask and try to answer certain questions:

    • What is the structure of the basin
    • Is the basin mature?
    • What is its burial and thermal history
    • What is it pressure profile
    • Any restructuration or secondary tectonics
    • Are there source and reservoir rocks, and seal?

    Our structural geologists analyse the structure of a basin and determine its tectonics setting and local structural features.  Following an increase in heat with depth as more sediments are supplied, a basin is said to mature at a given temperature.

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  • PORE PRESSURE PREDICTION

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    This is the heart of drilling technology. The aim of pore pressure prediction is to prognose the pressure in the shale.  That in the sandy reservoir is assumed to be close to the overlying and underlying shale (where the sand pressure is in equilibrium with that of the shale.  Regional knowledge and comparison with offset well is used to predict shale in the sand or carbonate reservoir.  Once we know the pressure in this shaly unit, it is possible to drill safely through them and hopefully, through the reservoirs whose pressures are relatively known from neighbouring well and measured while drilling.

    Pressures in shale can only be calculated, or predicted, not properly measured with a tool. Pressure can be predicted before drilling (Pressure prognosis) and or while drilling (Pressure While Drilling – PWD).  Logs measured while drilling, including resistivity and sonic logs, give indication of how compacted the shales are, thereby giving an indication of what their pore pressures could be. That is where compaction or undercompaction is the main cause of overpressure.

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  • PETROLEUM EVALUATION

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    Petroleum prospect is made up of a combination of a combination of some features necessary to have a petroleum accumulation.  Once these features are combined, the only missing to make of the “five fingers of the palm” that holds the black gold, is the petroleum itself.  These four features are:

    1. The Source

    2. The Seal

    3. The Trap

    4. The Reservoir

    First stage prospect evaluation

    At the initial stage of the prospect evaluation, we ask and try to resolves certain questions:

    • Is the source rock mature?
    • What is the evidence that generated oil has migrated to the reservoir?
    • How good is the reservoir?
    • Is the trap structure fractured?
    • Was the trap available before the charging?
    • Or has the oil be migrated away before the formation of the structre
    • Any recent tectonics that might have destroyed the prospect<
    • What is the seal efficiency and integrity?
    • Has the oil or gas leaked?
    • What are the main risks and uncertainties?

    And many more such questions…

    At the second stage of the process, we are risking the prospect and estimating the uncertainties.  At the end, we provide a prognosis for drilling the well, prediction of the depth, thickness and information on the units that will be found when a well is drilled through a prospect.  This is known as well prognosis, and it is the ultimate document that gives important geological and reservoir information that will include factors such as:

    • Lithology of formations
    • Reservoir tops and markers
    • Fluid types and contacts
    • Fluid (gas-water-oil) properties
    • Pore Pressure predictions

    Seal Analyses

    The first thing is seal evaluation is to determine type and distribution.  A shale seal for example, if thick enough, has a high tendency to seal. But this is not always the case as the presence of fractures could compromise the seal.  No seal is completely sealing or completely leaking.  It is the degree of competency that is tested in seal evaluation.  The seal efficiency test the leakage through capillary entry into pore throats in the seal, while integrity tests the resistance of the seal to microfracturing under a given pressure.

    Our seal evaluation uses seismic, log data, fluid sampling, core data and pressure or temperature values to infer seal behavious with respect to underlying reservoirs.  Seal and reservoir conditions, reservoir types and source of hydrocarbon are taken into consideration in the analyses. We provide reports to predict both Seal Efficiency (Capillary Entry) and Seal Integrity (Top Seal Hydrofracture).

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