Filtration tests in exploration and extraction of crude oil

Filtration tests are used extensively in the oil industry for analyzing particles in drilling fluids and extracted oil. In this blog, we explore where these filtration tests are used and how they ensure reliable extraction of crude oil.

The petroleum industry generates fuels and products that power the world’s economy. Here we will look at some of the most fundamental processes in oil extraction and discover how filtration tests give engineers the information they need for successful oil extraction.

The first stage in the oil exploration and extraction process requires locating crude oil underground, which is achieved using sophisticated geophysics techniques such as seismic surveys. After potential sites for extraction have been identified, an exploration well is drilled to determine the presence or absence of crude oil.

Various liquids are used in oil well drilling, and all must have a tightly controlled composition. Scientists regularly measure the level of suspended solids in drilling fluid, as a certain level of particulates is needed for borehole stability.

Filtration analysis is also used to assess the levels of bacteria in water used for hydraulic fracturing. This provides scientists the data necessary to efficiently control subsurface microbial growth that can hinder oil extraction from wells.

Another important use of filtration analysis in the oil industry is the testing of crude oil for specific contaminant particles, including bitumen and asphaltenes, which might be more abundant in oil from some locations than others. Testing data guides the type and levels of dispersant required and determines downstream processing parameters such as temperatures and pressures.

The methods provided by filtration tests are rapid and convenient, and can often be performed in the field, making them important during oil well construction.

Testing of drilling fluid helps prevent borehole collapse

Drilling of wells for exploration and extraction requires pumping fluids down the inside of the drill pipe: these fluids then travel upwards along the walls of the borehole. The drilling fluids:

• Keep the drill bit cool and lubricated,
• Lift dislodged rocks from the hole,
• Equalize pressure to prevent fluids from flowing into the borehole

The drilling fluid, which is a kind of slurry formed of water or oil-based mud, forms a ‘filter cake’ on the walls of the borehole. This filter cake prevents loss of drilling fluid into surrounding porous formations and also prevents invasion of solids into the borehole.

The importance of the filter cake for borehole integrity requires engineers to perform extensive testing of the drilling fluid, most often using the high temperature high pressure (HTHP) filtration test. Testing the fluid loss properties of the drilling fluid with the HTHP test is essential for borehole stability and ensuring steady and reliable extraction of oil from a well.

This test is conducted using an HTHP filter press, which uses a controlled pressure source and a heating jacket to subject the drilling fluid to conditions matching those in the borehole. The filter press then filters the drilling fluid through membrane filters with fine particle retention, such as Whatman™ GF/A glass microfiber filters, and the amount of filtered fluid is measured to assess the cake-forming characteristics.

Efficient hydraulic fracturing requires bacterial control

Hydraulic fracturing (or ‘fracking’) is a variant of the standard method of oil extraction that involves drilling into the earth and pumping high pressure fracturing fluid made of water and chemical additives into the well. This high-pressure fluid produces fractures in the underlying rock that then grow over time, releasing oil that can be extracted.

While useful for extracting oil from traditionally harder to reach deposits, fracking operations also provide a perfect breeding environment for sulfide-producing bacteria. The proliferation of these bacteria can lead to several problems during oil extraction, including:

• The need for expensive downstream hydrogen-sulfide removal from oil
• Microbially influenced corrosion (MIC) of underground pipes
• Difficulty extracting oil as bacterial biomass accumulates in fractures

To prevent these issues affecting production, scientists regularly test fracking water for bacteria using filtration analysis, enabling the selection of site-specific biocides preventing bacterial growth within the system. These analyses can be performed using Whatman™ sterile cellulose membranes with a pore size of 0.45 µm, as recommended by the Association for Materials protection and Performance (AMPP), a regulatory authority in the oil and gas industry that issue standards for tests used in the oil exploration and extraction stage.

Summary

Petroleum exploration and extraction provides the raw material for a range of downstream petroleum products. Membrane filters and their associated tests help monitor the fundamental processes of borehole drilling and oil extraction to ensure smooth operations and keep the oil wells profitable in the long term.

For more information about filtration offerings, visit our lab filtration knowledge article page. For support with your filtration or to ask a question about any of the applications covered, contact our scientific support team.