Work

Experimental study on in-situ self-generating proppant fracturing prepad fluid system for micrometer-scale fractures in calcium-rich reservoirs

Year: 2025

Type: article

Abstract: Conventional proppants effectively maintain primary and near-wellbore fracture apertures, but cannot access far-field micron-scale fractures (≤150 μm), which are prone to closure leading to reduced fracture conductivity and impaired hydrocarbon recovery efficiency. This study proposes an innovative system based on the injection of a phosphate-based prepad fluid into reservoir fractures, where it hydrothermally reacts with calcareous minerals to form hydroxyapatite (HA). This technology aims to overcome propping challenges in far-field micron-scale fractures of calcium-rich reservoirs. This study considers the design and optimization of the proppant system, evaluates the factors influencing proppant growth, and uses lab-scale experiments to assess proppant strength and performance. Reaction mechanisms were elucidated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that hydrothermal reactions between calcareous minerals and phosphate systems ((NH 4 ) 2 HPO 4 , NH 4 H 2 PO 4 , NaH 2 PO 4 ) achieve HA yields exceeding 90 %. Orthogonal experiments revealed that the order of significance for factors affecting self-growth performance is: reaction temperature > initial pH > phosphate concentration > reaction time. The optimal set of conditions to achieve maximum HA yield was determined to be a phosphate concentration of 5 wt%, reaction time of 48 h, reaction temperature of 120 °C, and initial pH of 2. Fracture flow conductivity experiments showed that rational optimization of the system formulation can lead to enhancements of up to 404 times in the short-term fracture flow conductivity, as well as enhancements of 80–110 times in long-term fracture flow conductivity. This significant improvement in conductivity validates the technical feasibility of this novel method.

Source: Results in Engineering

DOI: 10.1016/j.rineng.2025.108243

Authors: Zengbao Wang, Yuwei Gan, Weian Huang, Huaqiang Shi, Junjie Jiang

Institution: China University of Petroleum, East China

Language: English

Topic: Hydraulic Fracturing and Reservoir Analysis

Subfield: Mechanical Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,940

Funders: National Natural Science Foundation of China, National Science and Technology Major Project