呼探1井井口压力波动特征及成因机理

呼探1井是准噶尔盆地南缘中段首口获得天然气勘探重大发现的超深层异常高压气井,该井在试采时井口压力出现大幅波动,无法有效确定储集层参数及开展合理产能评价。因此,基于颗粒架桥堵塞原理,利用气藏动态分析法,表征了裂缝中颗粒循环堵塞—解堵变化趋势;同时,建立呼探1井双重介质渗流机理模型,开展压力波动特征分析及成因机理研究。研究表明,裂缝中颗粒循环堵塞—解堵是造成压力大幅波动的主要原因,一方面,随着裂缝中颗粒不断运移解堵,压力波动幅度逐渐减小,表皮系数逐渐减小,采气能力趋于稳定;另一方面,在裂缝循环堵塞—解堵的过程中,裂缝开度越大,压力波动幅度越大,同一裂缝开度下,近端裂缝堵塞—解堵,导致压力波动幅度较大,远端则相反。不仅为准噶尔盆地南缘中段储集层特征研究、井位部署、产能评价提供依据,而且为超深层异常高压气井压力分析提供借鉴。

Characteristics and Genesis Mechanism of Wellhead Pressure Fluctuation for Well Hutan-1

Well Hutan-1 is the first ultra-deep and abnormally high-pressure gas well that revealed a significant discovery in gas exploration in the middle section of Junggar basin’s southern margin. However, during the production test, the wellhead pressure of this well fluctuated greatly, making it impossible to effectively determine reservoir parameters and reasonably evaluate productivity. Based on the principle of particle bridging and plugging, and by using the gas reservoir dynamic analysis method, the variation of cyclic plugging and unplugging of the particles in fractures was investigated, and a dual-medium flow model for Well Hutan-1 was established for analyzing the characteristics and genesis mechanism of wellhead pressure fluctuation in the well. The research shows that the cyclic plugging and unplugging of the particles in fractures is the main reason for the large pressure fluctuation. With the continuous migration of the particles and unplugging in fractures, the pressure fluctuation amplitude and the skin factor gradually decrease, and the gas productivity tends to be stable. During the cyclic plugging and unplugging of the particles in fractures, the greater the fracture aperture, the greater the pressure fluctuation amplitude. Given the same fracture aperture, the proximal fractures are plugged and unplugged, resulting in a great pressure fluctuation amplitude, while the opposite is true at the distal fractures. The research provides a basis for the study of reservoir characteristics, well deployment, and productivity evaluation in the middle section of the Junggar basin’s southern margin, and provides a reference for analyzing pressure fluctuation in the same type of ultra-deep and abnormally high-pressure gas wells.