Research and Application of a Controllable Permeability Refracturing Technology in a High-Water-Cut Potential Layer

Abstract

Summary The Fuyu oil field is a typical shallow, low-temperature, low-permeability reservoir. At present, the oilfield composite water cut is 95%, artificial fractures interlace with natural fractures, and the distribution of ineffective circulation channels between wells is complex. This paper found that after reducing the permeability of the original fracture, refracturing can effectively improve the longitudinal extension range of the new fracture through numerical simulation. Therefore, a controllable permeability temporary plugging agent is studied, and controllable permeability refracture technology is proposed. The controllable permeability temporary plugging system is composed of elastic particles, quartz sand, and quick-soluble elastic enhancers, which are based on elastic particles that do not age, and long-term plugging can be achieved. Through physical experiments, 0.5–1-mm elastic particles with 70–140 mesh and 16–30 mesh quartz sand were used in different ratios (i.e., 5:5, 6:4, and 7:3). According to the closure pressure and the permeability of the fracturing layer, the ratio chart of elastic particles and quartz sand is established. The controllable permeability refracture technology can select the ratio of the quartz sand and elastic particles according to the closure pressure and the control requirements of the fracturing horizon permeability. Through field applications, we found that, compared with the conventional refracturing technology, the average daily fluid gain per well decreased from 5.0 to 3.9 tons, and the daily oil gain increased from 0.3 to 0.6 tons. The controllable permeability fracturing technology could reduce the permeability of the original fracture and improve the vertical production degree of the reservoir after refracturing. In addition, this method ensures that the original fracture has a certain conductivity and that the high-permeability layer reserves are not lost due to temporary plugging agents, thus expanding the planar sweep volume and effectively improving reservoir recovery. Nevertheless, the chart established is mainly suitable for shallow reservoirs, and the closure pressure is 3–15 MPa in this paper. Further testing and research are needed for deep reservoirs.

Research and Applications of New Fracturing Technology in Low-Abundance and Greater-Depth Well LN-1 Reservoirs

“…The productivity of low-abundance reservoirs can be improved after fracturing, so new fracturing technology has received more and more attention. In view of the geological characteristics of the Fuyu oilfield, such as shallow burial depth, low temperature, low pressure, and low permeability, as well as the development characteristics of high-composite water content (95%) and the interlacing of artificial and natural fractures, Qi et al [28] proposed a new method of refracturing with controllable permeability. The formulation of a temporary plugging agent with controllable permeability was optimized.…”