Fracturing Innovations Propel Yingxiongling Shale Oil Development
To promote innovation and practical application in shale oil development technologies, the Oil & Gas Process Research Institute of Qinghai Oilfield held a technical exchange meeting on June 5–6 focusing on fracturing practices at the Yingxiongling shale oil platform wells.
Centered around the themes of "clarifying mechanisms, building standards, targeting layers, and designing plans," the meeting emphasized geological-engineering integration. In-depth discussions were held on Yingxiongling's geological characteristics, fracturing practices in platform wells, and technological breakthroughs. Zhang Yongshu, General Manager and Deputy Party Secretary of the oilfield company, attended along with experts and officials from China University of Petroleum (Beijing), the Exploration Division, and the Research Institute of Exploration and Development, offering strategic guidance for the efficient development of Yingxiongling shale oil.
Geological Characteristics Discussion:
Clarifying Reservoir Properties to Pinpoint Development Targets
The Yingxiongling shale oil reservoir is characterized by a "massive mountainous saline lacustrine mixed lithology," exhibiting four main traits: low-TOC shale hydrocarbon generation, massive reservoirs, high fracturability, and low saturation. The upper section of the Xiaganchai Formation has a thickness exceeding 1,200 meters, making it the thickest developed shale oil belt in China. However, 97% of samples have TOC <2%, and oil saturation is only 30–60%.
Global comparisons reveal discrepancies between source rock quality and engineering suitability, as well as preferences between reservoir and fluid qualities. Despite challenges such as large stress differentials and fracturing pressures exceeding 80 MPa, the low clay content and favorable porosity present opportunities for effective reservoir stimulation. The Xiaganchai block has identified three "sweet spots" (sections 5, 14, and 15) with high and stable yields verified through horizontal drilling, including the Chaiping-1 well’s Section 5, which yielded 113 barrels per day on test.
Fracturing Technique Iteration:
From Scale Optimization to Precise Fracture Network Control
Yingxiongling has undergone three major fracturing process upgrades. The Yingye-1H platform initially used close well spacing (200–300 m) and high fluid intensity (30.3 m³/m) with a "tight cutting + large-section multi-cluster" design. However, severe inter-well interference resulted in low daily output (20 tonnes) and high water cut (91%).
A five-dimensional optimization strategy was later developed: increasing well spacing to 500–600 m, reducing fluid intensity to 29–32 m³/m, adjusting displacement to 16–18 m³/min, limiting clusters per stage to 4–6, and employing "simul-frac + zipper fracturing." On Yingye-3H, this improved fracturing efficiency to 3.9 stages/day. While still behind North America’s 10–14 stages/day, innovations like "sloped perforation + combined temporary plugging" raised cluster activation from 59.6% to 89.8%, with 25% improvement in fluid distribution.
Supporting Technological Innovations:
Full-Process Enhancements to Ensure Effective Stimulation
A four-dimensional monitoring system was established: fiber optics outside casing to detect fracture width, high-frequency pressure monitoring for inter-well interference, downhole microseismic to delineate fracture networks, and tracer analysis for fluid contribution. For instance, during fracturing of Yingye-3H15-4, fiber optics detected a 26.7 MPa pressure rise in neighboring well 2H14-2, confirming natural fracture connectivity of up to 1,252 meters. This data-informed "pre-frac prevention, real-time adjustment" approach reduced well interference on 3H platform by 40% compared to 2H.
Temporary plugging applied a dual-layer strategy: intra-stage 5+ clusters used composite ball types (18/22/25 mm) at 50% fluid volume, while intra-fracture redirection used 1–3 mm agents at 30% and 70% of fluid volume.
Well testing adopted a three-phase pressure control approach: 15-day shut-in until pressure drop <0.1 MPa/day before opening; initial 2.5 mm choke used until fluid returns reached 120 m³/day, then expanded to 3.5 mm.
Eight-Dimensional Enhancement Plan:
Technical Roadmap for Breakthroughs
To address current bottlenecks, an eight-pronged enhancement plan was proposed:
Strengthening R&D
Expanding efforts
Innovating fracturing tech
Enhancing customized design
Fortifying anti-interference measures
Developing fluid systems
Building comprehensive support
Deploying cost-reduction equipment
Three innovative fracturing techniques will be piloted:
CO₂ Precharged Fracturing: Carbonate dissolution lowers breakdown pressure by 15–20%.
Infinite Sliding Sleeves + Single-Cluster Tight Cutting: Cuts pump truck demand by 50%, reduces operation time by 37%.
Upgraded Temporary Plugging Diversion: Uses supramolecular phase-change diverters to boost fracture complexity by 1.5×.
The "three-barrier" anti-interference system includes:
Pre-frac shut-in for pressure build-up
Simul-frac + zipper construction during fracturing
Post-frac temporary ball agents to seal fractures
Expert Dialogue and Future Direction
After hearing reports, Zhang Yongshu addressed three core issues:
Why do single horizontal wells achieve high output while platform wells underperform?
What underlies frequent fracture interference?
Why does productivity fail to recover after well reactivation?
Experts from China University of Petroleum (Beijing) responded with dual-perspective insights:
Utilize natural fractures and complex textures to build 3D fracture networks;
Optimize perforation location and proppant scale via collaborative modeling to control fracture morphology;
Establish a productivity attribution model based on microseismic, pressure testing, and fiber-optic data to decode high-output well characteristics.
Participants concluded the next phase would focus on dynamic geo-engineering coupling, multi-scale fracture modeling, and full-life-cycle productivity forecasting to overcome shale oil development barriers and support deep resource exploitation.
