RealView Studies

Measure wax and asphaltene deposition from live reservoir fluids at field conditions

Changes in pressure, temperature, or oil composition often induce precipitation that can lead to deposition of organic solids in production and transportation pipe. Production system design and operating strategy must provide for control and remediation of those deposits.

For RealView live solids deposition studies, Schlumberger uses a new lab-scale apparatus that bypasses the limitations of conventional deposition measurement techniques by mimicking the process of wax and asphaltene deposition from live reservoir fluids under realistic production and transportation conditions.

RealView studies allow independent variation of test parameters to quantify the effects of pressure, temperature, composition, surface type, flow regime, and shear on the deposition behavior of waxes and asphaltenes.

System capabilities

Unlike conventional flow loops, RealView studies measure live oil deposition in turbulent flow, with temperature control from 4 to 150 degC [39 to 302 degF] and high-pressure adaptability to 103 MPa [15,000 psi]. The cell is suitable for testing sour fluids and requires a sample volume of only 150 ml per test run.

Laboratory apparatus

The RealView apparatus comprises a test cell, a control system, and a circulation system, all of which are housed on a control bench. The test cell consists of a cylindrical vessel with an axially centered heat source. The outer wall of the vessel is stationary, and the inner wall, or spindle, rotates to create a turbulent or laminar flow regime in the annular space.

In addition to allowing precise and independent control of pressure, temperature, differential temperature, and spindle speed, the deposits are collected for quantification and qualification using high-temperature gas chromatography for waxes and saturate, aromatics, resins, and asphaltene analysis for asphaltenes. Deposit mass is then used to calculate a deposition rate based on the cell surface area and test run time.

The deposition rate can be used to scale up to the field, or Schlumberger can provide OLGA 5 simulation results for wax buildup over time using the improved input coefficients based on live oil deposition data from the RealView cell.

RealView studies offer the only direct laboratory measurement of organic solids deposition tendency that can be translated to the field. They can help assess the risks and costs of control and remediation to determine whether to develop a prospect.

The RealView cell, which Schlumberger developed through a multiyear, joint-industry project with Shell, has demonstrated a repeatability level of ±15% in extensive testing. The cell enables study of deposition from live fluid at turbulent flow for results that can realistically be correlated to actual field conditions. Therefore, the data obtained allow production system design decisions to be made with greater certainty. Significant cost savings can be realized through less conservative design and optimization of remediation techniques, particularly in offshore production environments.

Deposition studies

In a typical RealView deposition study, the operator sets the test apparatus at the anticipated production conditions where solids will be present, then selects the number of test points and operating conditions for which deposition data are needed to

• improve scaling to the field
• study the effects of various system designs (the amount of insulation)
• study the effects of production operations, including chemical selection and the introduction of gas lift.

Studies performed on asphaltenic oils are primarily run at isothermal conditions, whereas wax deposition studies are performed maintaining a differential temperature between the fluid within the chamber and the outer wall. After an estimate of the deposition rate is made, a sample can be taken to characterize the chemical composition of the deposit.

Powerful information for planning

RealView wax and asphaltene deposition testing using live oils allows

• study of wax and asphaltene deposition along a production path under turbulent flow
• sensitivity studies of a single deposition parameter
• determination of deposition rate by quantifying amounts deposited per run
• examination of the composition of wax and asphaltene deposits
• measurement of data that can be scaled to pipeline
• generation of data that can be input to OLGA 5 simulation software to model wax buildup over time for system design.

Real savings potential

RealView live solids deposition studies can help you achieve significant reductions in capex and opex through

• study of the effects of chemical additives on actual deposits under representative conditions
• more realistic deposition of wax and asphaltenes at field conditions for more accurate systems modeling
• study of deposition mechanisms for optimized completion designs.

Benefits

Efficient production operations through optimized

• system design
• chemical selection, dosage, and treatment
• pigging frequencies and remediation strategies