Reservoir characteristics and effective development technology in typical low-permeability to ultralow-permeability reservoirs of China National Petroleum Corporation

Abstract

Low-permeability to ultralow-permeability reservoirs of the China National Petroleum Corporation are crucial to increase the reserve volumes and the production of crude oil in the present and future times. This study aimed to address the two major technical bottlenecks faced by the low-permeability to ultralow-permeability reservoirs by a comprehensive use of technologies and methods such as rate-controlled mercury injection, nuclear magnetic resonance, conventional logging, physical simulation, numerical simulation, and field practices. The reservoir characteristics of low-permeability to ultralow-permeability reservoirs were first analyzed. The water flooding development adjustment mode in the middle and high water-cut stages for the low-permeability to ultralow-permeability reservoirs, where water is injected along the fracture zone and lateral displacement were established. The formation mechanism and distribution principles of dynamic fractures, residual oil description, and expanding sweep volume were studied. The development mode for Type II ultralow-permeability reservoirs with a combination of horizontal well and volume fracturing was determined; this led to a significant improvement in the initial stages of single-well production. The volume fracturing core theory and optimization design, horizontal well trajectory optimization adjustment, horizontal well injection-production well pattern optimization, and horizontal well staged fracturing suitable for reservoirs with different characteristics were developed. This understanding of the reservoir characteristics and the breakthrough of key technologies for effective development will substantially support the oil-gas valent weight of the Changqing Oilfield to exceed 50 million tons per year, the stable production of the Daqing Oilfield with 40 million tons per year (oil-gas valent weight), and the realization of 20 million tons per year (oil-gas valent weight) in the Xinjiang Oilfield.

Integrated Design Technology of Geological Engineering for Pressure Flooding and Water Injection in Low Permeability Reservoirs: Take the Reservoir of Keshang Formation in Wu2 East Area as an Example

“…Based on the geomechanical model of the well group, the complex fracture network simulation of geological engineering integration is carried out, and the hydraulic fracturing simulation is carried out according to the pumping program data of oilwater well fracturing construction, and the fracture network models of seven oil wells and two peripheral water injection wells inj2 and inj6 are established (Figure 2). On the basis of this model, the unstructured grid subdivision technology is adopted to finely characterize the simulated fracturing in the form of unstructured grid, and a three-dimensional unstructured grid numerical model (Figure 3) is established, so that the dynamic and static information of fracturing simulation, production history fitting, and prediction can be seamlessly connected [4].…”

Study on the Profile Control and Oil Displacement Mechanism of a Polymer Nano-microsphere for Oilfield

“…Reservoirs with low permeability in China have complex pore structures. − There are some problems such as severe water channeling and low oil recoveries during the water injection development. − Technologies of conventional plugging and profile control cannot meet the production demands of oilfields. − Polymer microspheres have attracted increasing attention in the area of depth profile control in recent years. − Polymer nano-microspheres have many advantages such as the small particle diameter, good elasticity, and deformation ability, making the microspheres easily reach the deep formation and selectively block the dominant channels of water flooding. − The permeability of the profound formation is changed, and the swept volume of the displacement fluid is enlarged due to the “migration-plugging-remigration-replunging” of microspheres. − …”

Study on an Anti-adsorption Micromaterial Tracer System and Its Application in Fracturing Horizontal Wells of Coal Reservoirs

“…Globally, technically recoverable unconventional resources amount to 6352.3 × 10 8 t, with technically recoverable natural gas resources accounting for 269.5 × 10 12 m 3 or 36.3% of the total. , Shale gas resources represent the largest unconventional natural gas source, boasting technically recoverable resources of 223.8 × 10 12 m 3 and recoverable coalbed methane resources of 38.7 × 10 12 m 3 . , In the development of unconventional oil and gas resources, horizontal wells are widely utilized due to their high productivity and large drainage area . Horizontal well staged fracturing has emerged as a crucial technical approach for developing unconventional oil and gas reservoirs, including low permeability reservoirs, tight reservoirs, and shale reservoirs. − …”