How Saudi Aramco discovered date-palm seeds could prevent lost circulation
Dr. Mohammad Amanullah, senior petroleum engineering consultant at Saudi Aramco’s EXPEC ARC, explains how he discovered that date-palm seeds were excellent lost circulation materials, and how his innovation could impact production
One afternoon in 2015, I tended the date-palm tree in my garden in Dhahran, Saudi Arabia. As I bit into a date, I realised that date-palm seeds have properties essential to lost circulation materials (LCMs), which reinforce porous downhole oil wells by bridging and plugging “thief zones,” rock formations that can divert expensive circulating fluids and drilling muds. Looking at the fallen palm leaves and pruning waste from my tree, I realised they too had potential as LCMs and formation-strengthening material.
The next day in my lab at Saudi Aramco’s Exploration and Petroleum Engineering Center/Advanced Research Center (EXPEC ARC), I set out with my team to test my theory.
The mother of many problems
LCMs aim to prevent non-productive time (NPT). The most frequent and costly problem during drilling is loss of circulation, where viscous drilling mud pumped into a well to stabilise it and push out rock chips partially returns to the surface, or does not return at all. In the worst-case scenario, the well can totally lose circulation, with no drilling fluid returning to surface. Given the high cost of operations, even a single lost-circulation event can mean a million-dollar setback, and mud loss is not easily predicted or prevented.
The complex subsurface, geomechanical, and geophysical characteristics of the rock can trigger other drilling problems. For the same reason that Saudi Arabia’s rock types make such good reservoirs, they are difficult to drill safely and economically due to the large quantities of drilling mud that can be lost. Borehole instability, or loss of structural integrity; kick and blowout, a discrepancy between wellbore pressure and formation fluids; and pipe sticking caused by pressure and mechanical issues can increase NPT.
A breakthrough in LCMs could do more than ensure safe, effective wells—it could turn the mother of many problems into the seed of many solutions.
ARC Plug: Planting a green idea
LCMs are made from natural materials like ground limestone, marble or formica that can strengthen the wellbore formation and prevent loss of circulation. Saudi Aramco has primarily used walnut shells (nut-plug) imported from the US. If my hunch was right, we could have a domestic alternative that would massively save import costs while supporting localisation.
With Saudi Arabia—the second-largest commercial date producer—generating 150,000 tons of seed each year, there would be an abundance of cheap, raw materials for manufacturing. The varied seed sizes from the kingdom’s 23mn registered date palms could be useful in a particulate LCM, thanks to a material toughness akin to the calcium carbonate sized particulate currently used by the oil and gas industry, as well as mechanical properties similar to nut-plug. The seeds’ organic nature also fits the industry’s emphasis on green products and additives that meet increasingly strict regional and global environmental protection laws, regulations, and standards. The physio-mechanical manufacturing process would incur no waste disposal cost, as the process generates no chemical or harmful waste, or by-products.
ARC Eco-Fiber: Using the rest of the tree
The date industry generates waste from pruning, harvesting, and production of commercial goods like date cookies. These natural fibers are eco-friendly, virtually non-toxic, and biodegradable. The yearly pruning of a single date palm can generate up to 10kg of dry leaves for fibrous LCM products, as well as large quantities of spikelets (stems used to make concrete). That figure does not include the thousands of diseased, non-productive, or dead trees disposed of each year. We decided to investigate the development of several grades of fibrous LCM products, which we would call ARC Eco-Fiber, recycling everything from roots to fronds.
Proving ARC Plug and ARC Eco-Fiber
Petroleum Engineer Mohammad Arfaj, my colleague in EXPEC ARC, led the next phase: testing our two LCMs. Starting with ARC Plug, physical tests measuring moisture content, specific gravity, bulk density and volumetric swelling created a baseline. Chemical and mechanical tests such as acid solubility and loss-on-grinding were done to characterise the date-seed-based sized particulate LCMs. A Permeability Plugging Test (PPT) apparatus was set to 1500 psi pressure and 250°F, simulating a well’s bottom hole temperature and pressure effect; and a 2-millimeter slotted disc represented a fractured loss zone. These conditions would demonstrate ARC Plug’s ability to efficiently seal and block the zone, in comparison to commercial nut-plug. A top cap with a slightly greater aperture was fixed for collecting any drilling fluid lost during the test interval. Then the seed and nut-plug LCMs were incorporated into a clay mud in concentrations of 10 pounds per barrel (ppb) and 30 ppb. The nut-based LCM showed poorer plugging potential at 10 ppb, with a significant volume of fluid loss but effective plugging at 30 ppb. ARC Plug, meanwhile, passed the test at both concentrations.
The Date Research Institute in Al-Hasa provided seeds from different trees and regions so that we could assess whether varying compositional, physical and mechanical characteristics could solve specific problems. Some of our date-seed LCMs showed instantaneous sealing capacity; the seed particles’ low density allowed the incorporation of much higher concentration of LCMs in the mud system.
Moving to ARC Eco-Fiber, trees and other waste materials were collected from various date farms and power-washed to remove soil, debris and other contaminants. The wood was chopped into 1.5 to 2-meter logs before grinding, and fibers were dried to bring moisture content under 4%, then graded into coarse, medium and fine. Two different muds were created, and PPT apparatus pressure was reduced to 500 psi and applied at the bottom of the test cell using a hand pump. A built-in heating jacket surrounding the test cell allowed heating the drilling mud to 250°F before applying pressure. Results indicated the suitability of date palm industry waste in replacing imported equivalent fibers and some synthetic fibers in commercial LCM blend design, and tests clearly showed that our newly developed date waste fibrous LCMs could seal loss zones containing up to 2mm fractures, with better or similar performance.
But perfection in the lab does not necessarily promise perfection in the field, as conditions vary. Yet three trials conducted in two different Saudi Aramco fields on three wells and hole sections prone to partial loss of circulation reinforced superior ARC results.
Environmental and economic gains
The tests also underscored the environmental value of organic date waste materials – essential in a changing energy landscape. A further environmental benefit addresses a serious issue for date-farming communities and manufacturers.
Date-palm biomass typically is burned, creating pollution, or buried, attracting insects and reptiles. The unplanned dumping of waste seeds containing date flesh and other nutrients provides a fertile breeding spot for pests that are extremely harmful to date palms, hindering tree growth and production. Also, discarded seed can germinate and interfere with crops. But plant-based ARC products can help protect the environment, as date seed is crushed to a biodegradable powder, and the fibrous waste’s ductile and malleability characteristics allow for less invasive drilling.
That is important as the shift of drilling activities from onshore to highly sensitive offshore and deep-water environments dictates green chemicals, LCMs and mud additives that avoid impacting the delicate marine ecosystem.
A market study initiated by our commercialization team found that the global drilling fluids and chemicals market is expected to reach $15.66bn by 2026. Anticipated uplift in oil prices after 2020 is expected to increase demand for drilling fluids and chemicals used in well drilling and completion, hydraulic fracturing and Enhanced Oil Recovery operations. The development of several chemical formulations to address environmental concerns will have an important impact and create demand for environmentally sensitive products like ARC Plug.
Sustainability is also aided by the renewable nature of the seeds and wastes, thanks to perpetually available local raw materials for particulate and fibrous LCM production. Localization is always more efficient, and newly viable commercial uses for date-farming byproducts can also prove a powerful catalyst for new jobs and related industries in the region. Right now more than half of Saudi Arabia’s discarded date seed is collected by Aramco, monetizing the product for the first time (and reflecting ample material for international as well as local use).
Likewise, the whole date-palm value chain profits. Collection and cleaning of fibrous waste – which could mean more than 1.75 million tons of material per year – is creating employment for unskilled labor, while the factory stages of drying, grinding, quality control, processing and packing can create new job opportunities each year. Delivering the products to the oil or gas field also adds job opportunity.
Following Aramco’s economic analysis and commercial strategy endorsement, prospective strategic partners were sourced to license, produce and sell ARC Plug technology. The local and regional advantages are clear, but global users also benefit.
ARC Plug’s local manufacture can mean a lower carbon footprint. A locally produced date tree LCM is transported at most only a few hundred kilometers to the rig site for consumption; however, imported products cross an ocean before making the same trek to the rig. In the field, date tree waste-based green additives are positioned at the forefront of drilling best practices around the globe. Currently, ARC Plug is applied for loss control. It will also be used as formation strengthening materials and sized LCM chips to control induced and severe losses associated with large fractures, cavernous channels, gaps and voids, for significantly higher economic advantage. Moreover, the use of other date palm wastes to produce fibrous and flaky LCMs will widen the application’s domain and economic benefits.
We are also expanding innovation for even more efficient, safe and sustainable drilling. Using ARC Plug materials, we’re developing a Rapidly Dehydrating Fluid, or RDF, that can handle a large thief zone by entering the gap as a liquid, expanding to fill the hole and creating a solid plug due to expulsion of the fluid phase by the pressure effect. In addition, date seeds can be potential raw materials for several products including fluid loss additive and eco-friendly fluid design.
The date palm industry has provided this region a livelihood for thousands of years. Likewise, the modern oil industry has powered economies and societies for nearly 200 years. It is fitting that this novel partnership should bring together these two venerable but seemingly disparate sectors, in the process enabling renewable innovation that sustainably solves the biggest oil and gas production challenge and affords people a better quality of life.