Oilfield Chemical Additives Application Cases

In 2022, in the face of the impact of the COVID-19 pandemic, the Northwest Oilfield Well Completion Management Center completed 24 projects, including oil well control equipment and heavy oil blockage pipe cleaning, saving procurement costs of 13.683 million yuan.

During the use of oil pipes, the pipe diameter becomes increasingly narrower due to the effects of wax, polymers, and salts, reducing the crude oil flow and affecting crude oil production. Therefore, drilling companies generally clean the pipes once a year. After treating the weld seams of the pipe joints, it is necessary to clean the pipes.

In general conditions, steel pipes used as oil pipes have rust on both the inner and outer surfaces. If not cleaned, this will contaminate the hydraulic oil after use, affecting the normal operation of the hydraulic devices. Therefore, it is necessary to remove the rust on the inner surface of the pipes through acid washing. Acid washing can also remove the rust on the outer surface of the pipes, which is beneficial for applying anti-rust paint to the outer surface of the pipes, providing long-lasting anti-corrosion protection. Acid washing is generally performed using an acid solution with a concentration of 0% to 15%. Youzhu Company, by providing corrosion inhibitor products:UZ CI-180,a high temperature resistant acidizing corrosion inhibitor for oilfield use. In the process of acidizing or pickling, the acid will corrode the steel, and at high temperature, the rate and range of corrosion will be greatly increased, therefore, in the oilfield production, the corrosion prevention of high-temperature pipe is particularly important, which is not only related to the benefits of oilfield exploitation, but also closely related to the production safety. The degree of acid erosion on pipelines and equipment depends on the contact time, acid concentration and temperature conditions, etc. UZ CI-180 has excellent high-temperature resistance, and at temperatures up to 350°F (180°C), the corrosion effect of acid on steel at high temperatures at the bottom of the well can be greatly reduced by adding UZ CI-180 to the acid mixture. Youzhu has received high recognition from the Northwest Oilfield Management Center for its projects in pipe cleaning, drilling fluid formulation, and equipment maintenance.

Located on Dong San Road in Dongying City, the Fengye 1-10HF well is the first shale oil horizontal well to break through the 20-day drilling cycle barrier, completing 24 days ahead of schedule. It is one of the three national shale oil demonstration zones approved by the National Energy Administration and the first national demonstration zone for continental fault basin shale oil in China. By completing the well 24 days ahead of schedule, over 10 million yuan was saved in costs.

Due to the proximity to a nearby well being fractured just 400 meters away and the proximity to the gravel rock boundary, the Fengye 1-10HF well faced risks of water intrusion, overflow, and fluid loss. Additionally, high temperatures at the well bottom posed challenges to various instruments. The project team focused on engineering technology support and tackling key technological issues. They successively solved constraints such as the difficulty in predicting strong heterogeneity sweet spots, limitations of instruments under high temperatures and pressures, and the coexistence of drilling fluid loss and influx.

They developed and applied a synthetic-based mud system to improve fluidity. Among these, the current drilling fluid additive TF FL WH-1 Cement Fluid-loss Additives,developed by Youzhu can form a high-quality film on the surface of the shale wellbore, preventing drilling fluid filtrate from entering the formation, TF FL WH-1 is designed for use in wells with bottom-hole circulating temperatures (BHCTs) in the 60℉(15.6℃) to 400℉ (204℃).

TF FL WH-1 provides API fluid loss control below 36cc/30min while controlling gas migration from the formation. Generally 0.6% to 2.0% BWOC is required in most slurries. It is usually used at a dosage of less than 0.8% BWOCthereby protecting the reservoir and stabilizing the wellbore. This effectively seals shale pores and microfractures, preventing drilling fluid filtrate from invading and reducing the transmission of pore pressure, significantly enhancing the inhibition of the drilling fluid.

Field application results show that the high-performance water-based drilling fluid is highly inhibitive, increases mechanical drilling speed, is stable at high temperatures, protects the reservoir, and is environmentally friendly.

In February 2022, Sinopec's Bazhong 1HF well, located in the Jurassic river channel sandstone oil and gas reservoir, innovatively proposed the "fracturing, imbibition, and well shut-in integration" fracturing design concept. This approach was developed to address the characteristics of dense river channel sandstone reservoirs and high formation pressure coefficients. The optimized fracturing technology, which includes "tight cutting + temporary plugging and diversion + high-intensity sand addition + imbibition oil enhancement," significantly enhanced the flow capacity of underground oil and gas and established a new fracturing model, providing a reference for large-scale fracturing of horizontal wells.

Youzhuo’s high-temperature fluid loss additive, high-temperature anti-collapse plugging agent, and high-temperature flow type regulator in the fracturing fluid overcome the pressure and fluid loss challenges caused by formation pore pressure, wellbore stress, and rock strength. The special gel plugging technology, derived from Southwest Petroleum University, allows the special gel to automatically stop flowing after entering the loss layer, filling fractures and void spaces, forming a "gel plug" that isolates the internal formation fluid from the wellbore fluid. This technology is highly effective for severe leakage in fractured, porous, and broken formations with significant fluid loss and minimal return volumes.

On May 30, 2023, at 11:46 AM, the Tarim Oilfield of China National Petroleum Corporation (CNPC) began drilling at the Shendi Teke 1 well, signaling the start of a journey to explore ultra-deep geological and engineering sciences at depths reaching 10,000 meters. This marks a historic moment for China's deep earth engineering, signifying a major breakthrough in the country's deep earth exploration technology and the beginning of the "10,000-meter era" in drilling capabilities.

The Shendi Teke 1 well is located in Shaya County, Aksu Prefecture, Xinjiang, in the heart of the Taklamakan Desert. It is a significant "deep earth project" by CNPC in the Tarim Oilfield, adjacent to the Fuman ultra-deep oil and gas area, which has a depth of 8,000 meters and reserves of one billion tons. The well has a designed depth of 11,100 meters and a planned drilling and completion period of 457 days. On March 4, 2024, the drilling depth of Shendi Teke 1 exceeded 10,000 meters, making it the world's second and Asia's first vertical well to surpass this depth. This milestone indicates that China has independently overcome the technical challenges associated with drilling ultra-deep wells of this magnitude.

Drilling at depths of 10,000 meters is one of the most challenging fields in oil and gas engineering technology, with numerous technical bottlenecks. It is also a key indicator of a country's engineering technology and equipment capabilities. Facing extreme downhole temperature and pressure conditions, significant advancements were made in high-temperature drilling fluids, high-temperature-resistant motors, and directional drilling technologies. Breakthroughs were also achieved in core sampling and cable logging equipment, ultra-high-pressure fracturing trucks with 175 MPa capacity, and fracturing fluid equipment, which were successfully tested on-site. These developments led to the creation of several critical technologies for the safe and efficient drilling and completion of ultra-deep wells.

In the drilling fluid system used in this project, specific high-temperature, high-pressure environments were addressed with the development of superior fluid loss reducers and corrosion inhibitors that maintain excellent rheological properties under high temperatures and are easy to adjust and maintain. Clay control additives also enhanced the dewatering capacity of clay particles under ultra-high temperature conditions, improving the adaptability and stability of the drilling fluid.

Jimusar shale oil is China’s first national terrestrial shale oil demonstration zone, located in the eastern part of the Junggar Basin. It covers an area of 1,278 square kilometers and has an estimated resource reserve of 1.112 billion tons. In 2018, large-scale development of Jimusar shale oil began. In the first quarter, the Xinjiang Jimusar National Terrestrial Shale Oil Demonstration Zone produced 315,000 tons of shale oil, setting a new historical record. The demonstration zone is accelerating efforts to increase shale oil reserves and production, with plans to complete 100 drilling wells and 110 fracturing wells by 2024.

Shale oil, which is oil attached to shale rock or within its fissures, is one of the most difficult types of oil to extract. Xinjiang has rich shale oil resources with broad prospects for exploration and development. China has identified shale oil resources as a key area for future oil replacement. Wu Chengmei, a secondary engineer at the Geological Research Center of Jiqing Oilfield Operations Area in Xinjiang Oilfield, explains that Jimusar shale oil is generally buried more than 3,800 meters underground. The deep burial and particularly low permeability make extraction as challenging as extracting oil from a whetstone.

China’s terrestrial shale oil development generally faces four major challenges: first, the oil is relatively heavy, making it difficult to flow; second, the sweet spots are small and hard to predict; third, the high clay content makes fracturing difficult; fourth, the distribution is inconsistent, complicating operations. These factors have long restricted the large-scale and efficient development of terrestrial shale oil in China. In the project, to treat fracturing flowback fluid, a new additive is used to reduce pollution and recycle the fluid, turning it back into fracturing fluid for reuse. This method was tested on nine wells in 2023 with excellent results. As of June 2024, the project plans to use the reconstituted fracturing fluid in a large-scale fracturing operation.

The main formation of the project consists of coal seams, gray and brown mudstone sections, which are water-sensitive formations. In the Jimusar shale oil block, the open-hole section of the second well is long, and the formation soaking time is extended. If water-based mud is used, collapse and instability are likely, but oil-based drilling fluids do not cause hydration effects. Oil-in-water emulsion drilling fluids, when stable, also do not cause hydration effects, thus oil-based drilling fluids do not create hydration swelling pressures. Research has led to the adoption of an oil-based mud system, with anti-collapse principles and measures as follows: 1. Chemical inhibition: Controlling the oil-water ratio above 80:20 to reduce water phase invasion into the formation, effectively preventing swelling and collapse of coal seams and highly water-sensitive formations. 2. Physical plugging: Adding weighting agents such as calcium materials in advance in weak formations to enhance formation pressure-bearing capacity and prevent well leakage. 3. Mechanical support: Controlling density above 1.52g/cm³, gradually increasing density to the design limit of 1.58g/cm³ in the build-up section. Weighting agents produced by Youzhu Company can achieve the desired effect, ensuring the smooth and successful completion of drilling and well completion projects.