A Comparison Between Seawater-Based and Freshwater-Based Fracturing Fluids
- Adam Wilson (JPT Special Publications Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- March 2017
- Document Type
- Journal Paper
- 46 - 47
- 2016. Society of Petroleum Engineers
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- 196 since 2007
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This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 182799, “Seawater-Fracturing-Fluid Development Challenges: A Comparison Between Seawater-Based and Freshwater-Based Fracturing Fluids Using Two Types of Guar Gum Polymers,” by Maryam Alohaly, Ahmed BinGhanim, and Raed Rahal, Halliburton; and Sabiq Rahim, Texas Tech University, prepared for the 2016 SPE Kingdom of Saudi Arabia Annual Technical Symposium and Exhibition, Dammam, Saudi Arabia, 25–28 April. The paper has not been peer reviewed.
Despite the lack of freshwater resources in the Arabian peninsula, fresh water is still used in unconventional-resource operations there. Seawater, however, is plentiful and could substitute for fresh water. The high salinity of seawater raises many chemical challenges in developing design criteria for fracturing fluids. This paper examines the chemistry of developing seawater-based fracturing fluids using two types of polymers as gelling agents and compares results to existing fresh-water-based-fracturing-fluid data under different conditions.
The oil and gas industry faces many challenges, including the availability of fresh water for making fracturing fluids, especially in the Arabian peninsula and other arid regions.
Using seawater to make fracturing fluid can help address several obstacles and reduce costs. However, using sea water to make fracturing fluids also poses several new challenges. The high salinity of seawater and its propensity for scaling, compared with fresh water, make it crucial to consider different factors and chemical properties that influence the process of developing fracturing fluid.
This paper presents issues that can arise when using seawater as a base to develop fracturing fluids with two different types of guar as the viscosifying agent—hydroxypropyl guar (HPG) and carboxy-methylhydroxypropyl guar (CMHPG).
Ion Composition of Seawater
The high concentration of sulfate in seawater affects ion pairings in sea water. Sulfate can form ion pairings with strontium, calcium, and magnesium. Fifty percent of the sulfate present in seawater is free ions that can interact with polymer chains. Mixing, evaporation, and precipitation can change with ocean depth or location, which affects the salinity of seawater around the world and in stratification within a specific region. The major-ion composition in open waters, however, is almost always the same because the oceans are well-mixed by currents.
The seawater in the Arabian Gulf can have significant evaporation rates, leading to hypersaline conditions; hence, the Arabian Gulf ’s major-ion content is very high. This is one of the major factors to consider when designing seawater-based fracturing fluids. Another challenge to consider is variation of salinity throughout the year in the Arabian Gulf.
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