Introduction Bottom Hole Sampling Mobile Laboratory Routine PVT Advanced Fluid Studies Analytical Chemistry Compositional Analysis What's New
Fluid transfer from formation test tools 25,000 psi DOT piston cylinders Onsite restoration and sample validation Separator sampling Onsite Measurement of API and GOR Onsite Measurement of CO2 and HS2 content Single-phase bottom hole sampling Mobile Laboratories

Reservoir Fluids

Core Lab is the leading provider of reservoir fluid services. Core Lab specializes in wellsite sample acquisition and transfer services, and laboratory PVT and Advanced Fluid studies. Core Lab has Mobile Laboratories for on-site reservoir fluid sample validation evaluations. Core Lab also provides ultra high-pressure DOT pistoned cylinders needed for the acquisition and storage of fluids from reservoirs with pressures up to 25,000 psi

Core Lab's range of services includes: Transfer of fluid samples from formation test tools Bottom hole sampling Surface separator sampling Sample restoration Separator sample recombination Routine PVT analyses Advanced Fluids studies, including miscibility, multi-contact, and EOR projects Flow assurance testing Mobile Laboratories for on-site evaluation of oil-base drilling fluid filtrate contamination of reservoir fluids and other initial sample quality checks Customized services and test programs

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Bottom Hole Sampling

Bottom Hole Tool Specifications:

Single Phase Sampling Tool Specifications - Wireline Operated The single-phase bottom hole sampling tool is a positive displacement design with a nitrogen accumulator to compensate for pressure drop during tool retrieval. This maintains a pressure on the sample (generally greater than bottom hole pressure) that prevents changes in density thus preventing precipitation of asphaltenes. Sample volume: 600 cc Maximum working pressure: 15,000 psi Maximum working temperature: 300°F Construction: 17/4 PH SS with H2S and CO2 service Length: 16.5 feet OD: 1 11/16" Weight: 86 lbs. Connections: 7/8" sucker rod

Positive Displacement Sampling Tool Specifications - Wireline Operated
The positive displace operation of this tool ensures no sample contamination due to the double O-ring seals in the sample chamber. The tool is triggered by a mechanical clock that is preset at the surface before running-in-hole. A 5-hour delay is standard, but a 10-hour delay is available upon request. The tools generally are run in tandem. Sample volume: 600 cc

Subsurface Sampling Using Positive Displacement (PD) or Single Phase (SP) Bottom Hole Sampler (BHS) Tools Subsurface Sampling Procedure Under-saturated oil reservoir fluids may be sampled at the surface separator or using subsurface samplers. However, if accurate gas-oil measurements cannot be obtained at the surface separator, subsurface sampling is the only means of collecting a representative reservoir fluid sample. Oil wells on gas-lift are also candidates for subsurface sampling.

Saturated oil reservoirs present special problems. Because of the potential loss of solution gas due to drawdown as the oil flows into the wellbore, saturated oil reservoirs are normally sampled at the surface separator. If this is not possible, the following conditioning procedure may result in representative samples.

Generally, the conditioning of a well for bottom-hole sampling depends upon the productivity index or draw-down of the reservoir pressure from static shut-in reservoir pressure to flowing bottom-hole pressure.

Since this varies greatly from one well or field to another, there is no universally correct method to condition all wells.

Representative bottom-hole samples can be obtained though, if two things are kept in mind. First, the sample must be taken at a pressure as near the existing pressure of the oil or flowing phase in the reservoir at the drainage limit as possible. Second, the sample must be taken at a time when the oil has been subjected to a minimum reduction in pressure in its movement into the well bore.

If productivity index information is available, it will usually dictate the conditioning procedure. When productivity index information is not available, the following general procedure is recommended for conditioning a well in preparation for subsurface sampling.

The rate should then be still further reduced to approximately one-half of the previous rate for the next twenty-four hour period, or, to as low a rate as the well can be produced and not load up with oil or water sufficient to stop production.

Finally, the well should be shut-in for twenty-four hours.

If it is not possible to obtain a rate of one-half the previous rate at any point, the well should be flowed at the lowest possible rate for the twenty-four hour period prior to shut-in.It should be noted that the rates mentioned above apply to a twenty-four hour period of steady production and not to any particular quantity of oil that might be produced during a shorter period of time at a higher producing rate.

Following the well conditioning, but prior to sampling, a measurement of bottom-hole pressure and temperature should be made in order to correlate laboratory data with reservoir data.

A pressure gradient should be determined during this measurement to locate the water level in the tubing, if one exists, and to determine the point of the gas-liquid interface.

Some engineers prefer to have a well flowing very slowly during bottomhole sampling.This is not recommended for the following reason: At a very low flow rate, the velocity of the fluids in the tubing may not be sufficient to sweep out any water that is possibly flowing into the well bore.

This water may accumulate in a considerable column near the bottom of the hole where it is desirable to trap the oil sample.Water samples, instead of oil, may be obtained under these conditions from a well, which has been flowing at a very low rate, although it may have had no prior record of water production.

The last accurate gas-oil ratio measurement, along with the separator conditions at which it was measured, should be submitted with the bottom-hole samples. This value will be used in the laboratory to verify that representative samples have been obtained.It is also useful in determining the state of the fluids in the reservoir at the time of sampling.

It is also recommended that the service company which obtains the samples, check the saturation pressure of each individual sample in the field.

By performing this test in the field, the service man can verify that duplicate samples were obtained. He should continue to take samples until he has obtained at least two with approximately the same saturation pressure.There may be times, because of extremely bad weather or other conditions beyond his control, when the service man will not be able to perform this test immediately.In such a case, it is recommended that he do so at the first available opportunity.

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Mobile Laboratory

Core Lab has over 30 years of wellsite sampling experience and provides a complete range of reservoir fluid services:

Core Lab's Onsite Mobile Lab, used extensively in the Gulf of Mexico, provides the following onsite services:

Fluid transfer from formation test tools Onsite restoration and sample validation Evaluation of oil-base drilling fluid filtrate contamination Compositional Analyses, Onsite Chemistry Sample evaluation, basic fluid properties (Flash test, API, GOR, gas analysis etc) Onsite in-situ viscosity measurements

Core Lab's Onsite Mobile Laboratory employs state-of-the-art technology to enhance the speed and safety of the Formation Test tool transfer process. SafeTran 3025 System FT chambers and tanks mounted on the restoration unit Simultaneous heated restoration of 3 large Formation Test tool chambers or multiple small tanks Controlled transfer of reservoir fluids from FT tool chambers into DOT cylinders Real-time computer acquisition of P&T data during opening pressure measurement, equilibration and restoration, and transfer SafeTran 3025 allows for 30 receiving cylinders to be mounted onto transfer manifold The manifold and all sample lines are heated Heated sample transport for up to 20 cylinders 30,000 psi sample transfer capability

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Routine PVT

Standard Reservoir Fluid (PVT) Study Packages: Oil reservoir study using surface separator samples Oil reservoir study using subsurface samples Abbreviated gas reservoir fluid study using surface separator samples Abbreviated gas reservoir fluid study using subsurface samples Constant volume depletion gas reservoir study using surface separator samples Constant volume depletion gas reservoir study using subsurface samples The range of services offered includes: Multi-stage separator tests for surface facilities optimization Extended chromatographic analyses (to C50+ for liquids) Compositional analyses Solids deposition Pipeline packages Water analyses Equation of State modeling

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Advanced Fluid Studies

The range of services offered includes: Enhanced oil recovery miscible displacements solubility swelling multi-contact studies gas injection revaporization waterflood studies interfacial tension studies Solids analysis and remediation paraffin characterization asphaltene onset scaling potential chemical inhibitors/chemical compatibility Flow assurance pipeline flow and fluid rheology solids precipitation blends and emulsions chemical additives corrosion testing Pressurized Fluids Imaging (PFI™) System isothermal depressurization (IDE) experiments P-T and P-x onset determinations chemical compatibility particle size distributions titration experiments EOS feasibility and characterizations modeling tuning

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Analytical Chemistry

Water Analysis Exploration and production water samples are routinely analyzed for API 12 ion composition, together with residual inhibitor, organic acids and tracer concentrations. Exploration waters are analyzed to determine a formation water composition, which is used in scale prediction and corrosion models. Routine produced waters are analyzed to determine the extent of contamination and scaling, and to assist in chemical squeeze programming. Scale/Deposit Analysis Samples of deposits from downhole production systems and pipelines are analyzed using sophisticated techniques including ICPAES, GC, SEM, EDX, XRD, FTIR and traditional wet chemistry. These results are used to determine composition, possible remedial treatments and control measures required to optimize production. Crude Oil Analysis Samples of crude oil and distillation fractions are analyzed to determine a variety of physical and chemical properties which affect the value and treatment of the oil. The tests are normally performed according to industry recognized IP, ASTM and UOP procedures. Physical Compatibility Studies Studies involving wax deposition, asphaltene flocculation, water and emulsion stability are performed to evaluate the compatibility of various mixtures. Chemical Evaluation Studies Studies involving wax inhibitors, asphaltene inhibitors, scale inhibitors and dissolvers, demulsifiers, biocides and pour point depressants are performed to determine the most efficient chemical and optimum concentration. Crude Assay Analyses Determination of boiling range distribution and cut-point yield analysis is provided for stock tank oils and condensates up to 575°C by ASTM D2892 and D1160 methodologies. Analysis can be performed to a D5236 series of specified temperature ranges or to carbon number boiling points.

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Compositional Analysis

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What's New

Pressurized Fluids Imaging (PFI™) System Core Lab recently updated "Best in Class" PFI™ system allows for a variety of imaging experiments including isothermal depressurization experiments, titration experiments, particle size distributions and solids onset determinations. Recent software, optical and operational upgrades only enhance the effectiveness of the prototype system.
SafeTran 3025 Core Lab's new formation test tool sample transfer module has the capability to connect thirty 25000psi cylinders in parallel for a continuous, safe transfer process. This transfer module is compact, easy to work with and a significant improvement in time efficiency and safety. Sample chambers can be allocated by a simple opening and closing of a valve, without ever disconnecting or re-connecting to the formation tool itself.
Wellsite Restorator A pneumatic rocking stand that holds two large Formation Test tool chambers. This unit fits into a compact 5ft x 5ft container.
25,000 psi DOT Pistoned Cylinders These are the highest pressure-rated DOT transfer and sample storage cylinders in the industry. 30 Cylinder Sample Restoration Chambers These large ovens allow us to restore up to 30 chambers / cylinders at one time.

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