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Study and Application of Stabilization and Differentiated Acidizing Stimulation System for Unconsolidated Sandstone Reservoirs
SHAO Shangqi, LI Shengsheng, LI Xiaonan
, Available online  
Abstract(104) HTML (74) PDF (2828KB)(19)
Abstract:
One of Middle East oilfield main production layers is a sandstone reservoir, primarily composed of sandstone and argillaceous siltstone. The rock is loose and prone to sand production. Conventional acidizing technologies are slow-acting and may even cause sand production. This paper analyze the mechanism of sand production and blockage in the reservoir, and develop a composite acidizing stimulation technology targeted at unconsolidated sandstone reservoirs. Based on the principle of "stabilization first, then stimulation," this technology can not only alleviate well blockage damage but also maintain reservoir stability. Through laboratory experiments, this paper developed a sandstone stabilizer suitable for high scouring flow rates. Under a flow rate of 1800 mL/h, the sand production rate can be stably controlled within 0.01%. Meanwhile, by applying the synergistic principle of different working fluid systems and aiming for "more scale removal, less sand dissolution," a differentially dissolving acidizing and descaling system was developed. Laboratory tests show that the dissolution rate of scale samples in the acid system is ≥95%, while the sand dissolution rate is <25%. The acid fluid can effectively alleviate the dissolution of sandstone minerals and maintain rock structure stability. Field tests have demonstrated that the composite acidizing technology, which follows the "stabilize first, then descale" approach, has increased average production and extended the treatment's effective period, effectively mitigating the problem of sand production in the reservoir. This provides a theoretical basis and practical direction for acidizing treatments in unconsolidated sandstone oilfields.
Research on Class Structural Environmentally Friendly Emulsifiers for Oil-based Drilling Fluids
CHENG Bingfang, WANG Chengjun, BU Fankang, BAO Linghan, WANG Chongchong, XIANG Peng
, Available online  
Abstract(400) HTML (314) PDF (3264KB)(20)
Abstract:
Using environmentally friendly ester derivatives such as epoxy fatty acid esters as raw materials, react with polyamines to form a main emulsifier with a Gemini surfactant structure. Then, using the main emulsifier as raw material, partially sulfonate it to form a multi class environmentally friendly emulsifier with a similar structure for oil-based drilling fluids. The molecular structure of the emulsifier was determined through infrared and mass spectrometry characterization, with a temperature resistance of up to 180℃, a demulsification voltage of over 900V, and an emulsification rate of over 90%. Capable of adapting to low oil-water ratio oil-based drilling fluid environments and drilling fluid systems formulated with different base oils. Adapt to drilling fluid systems with different densities. Has excellent biodegradability. A method for evaluating the microstructure of emulsion droplets was established to determine the stability of emulsion droplet formation, and it was determined that high emulsifier dosage can effectively improve the uniformity and high-temperature stability of oil in water emulsion droplets.
Flow Characteristics of Dual-Increasing Stimulation Slurry in Unconsolidated Silty Sandstone
LIU Xilong, SUN Qian, ZHANG Guobiao, LI Bing, ZHANG Kewei
, Available online  
Abstract(1141) HTML (895) PDF (7827KB)(30)
Abstract:
The dual-increasing stimulation slurry is a novel stimulation fluid developed for weakly cemented reservoirs, such as submarine methane-hydrate-bearing silty sandstones. After injection into the formation, it consolidates to form porous-media slurry veins that enhance permeability. This study employed a slurry fracture flow visualization apparatus to investigate the flow characteristics of the slurry within muddy silty sediments. The experiments revealed the influence of geological parameters, slurry formulation, and operational parameters on slurry flow, fluid loss, and slurry-vein porosity. The results indicate that the slurry flows uniformly and exhibits a convex fracture flow profile, flowing to the end of main fracture and branch fracture, effectively filling fractures. Lower fluid loss increases the proportion of medium-to-large pores within the slurry veins. Adjusting the slurry formulation can reduce fluid loss in formations of varying permeability, whereas a high injection rate expands the fluid loss zone. The effective porosity ranges from 50% to 60% with a uniformly distributed pore space, forming a structure dominated by large pores (pore diameter > 50 nm) and densely distributed micro- to mesopores (pore diameter < 50 nm). This pore network can serve as high-conductivity channels for gas and water migration, while the dense distribution of small and medium pores is conducive to sand control.
A New High-temperature Tackifier for Solid-free Drilling Fluids
ZHOU Guowei, ZHANG Xin, YAN Weijun, HUA Guiyou, ZHUANG Zhenhua, QIU Zhengsong
, Available online  
Abstract(1061) HTML (850) PDF (2972KB)(34)
Abstract:
The Ordovician buried-hill reservoir in Liaohe Oilfield exhibits a challenging high-temperature (200℃ at reservoir center) and low-pressure (pressure coefficient 1.01～1.06) environment characteristic of typical high-temperature, low-pressure oil/gas reservoirs. To achieve formation protection, a solids-free water based drilling fluid was prioritized, with tackifier selection being critical. Through molecular structure optimization, a novel high-temperature/salt-resistant tackifier was developed using four monomers: N-vinylpyrrolidone (NVP), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N'N-diethylacrylamide (DEAA), and 1-(3-sulfopropyl)-2-vinylpyridinium hydroxide inner salt. The synthesis employed N'N-methylene bisacrylamide as crosslinker with potassium persulfate and sodium bisulfite as redox initiators. FTIR and TGA analysis confirmed successful polymerization, demonstrating superior thermal stability with 296.66℃ initial decomposition temperature and only 45.96% mass loss during degradation phase, outperforming commercial HE300. The fluid achieved remarkable rheological performance with 722 consistency coefficient (K) at 0.5% concentration. Laboratory evaluations verified exceptional thermal stability up to 220℃ and saturated salt tolerance. Field applications demonstrated excellent viscosity-enhancing performance and robust durability of this novel tackifier, providing vital technical support for buried-hill reservoir development and high-temperature formation drilling operations.

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