关于超深油气井完井工程与油气藏采收率的思考

Reflections on Completion Engineering and Recovery of Ultra-deep Oil and Gas Wells

超深油气藏的不断开发采收率与油气井的完井设计紧密相关。然而,由于钻井装备的限制、高压盐水层的存在、地层易垮塌和易漏失等开发特性以及经济评价因素的考量,超深油气井的完井方式多样(如裸眼完井、不超过ϕ127 mm小尺寸油层套管完井等);生产管柱穿越射孔顶界乃至射孔底界的设计;多选用永久型封隔器等,这些都可能增加生产作业的难度、延长作业时间和提高作业成本,并影响开井率和最终采收率。选取两个已投入开发的超深油气藏区块作为案例,分析发现砂或泥砂埋积是导致开井率低下的重要原因,进而对采收率产生不利影响。研究提出超深井完井的研究与设计应预设出砂或泥砂埋积的情景,旨在延长砂或泥砂埋积的时间,以便为后续作业创造有利条件,最终目标是提高采收率。为此,研究从完井方式、油层套管尺寸、完井管柱配置、封隔器类型选择以及沉砂口袋设计等5个关键方面进行了深入的科学研究与优化设计。在此基础上,进一步对钻完井投资、钻完井周期及经济评价指标进行了综合测算。若经济评价指标未达预期,则通过提升单井产量来解决建井质量提升与经济评价之间的潜在矛盾。

The continuous development of ultra-deep oil and gas reservoirs is closely related to the completion design of oil and gas wells.However,due to limitations in drilling equipment,the presence of high-pressure saline layers,geological characteristics such as prone-to-collapse and prone-to-leakage formations,as well as economic evaluation considerations,the completion methods for ultra-deep oil and gas wells exhibit significant diversity(open-hole completions,completions using small-sized reservoir casings not exceedingϕ127 mm,and so on).Designs featuring production strings traversing the perforation top boundary and even the perforation bottom boundary are also common,and permanent packers are often preferred.These factors can potentially increase operational difficulties,prolong operation times,elevate costs,and impact well productivity and ultimate recovery rates.By analyzing two already developed ultra-deep oil and gas reservoir blocks as case studies,it was discovered that the accumulation of sand or silt is a crucial factor contributing to low well productivity,subsequently adversely affecting recovery rates.In response,the study proposes that the research and design of ultra-deep well completions should anticipate scenarios of sand or silt accumulation.The objective is to prolong the duration of sand or silt accumulation,thereby creating favorable conditions for subsequent operations and ultimately enhancing recovery rates.To achieve this,the study conducted thorough scientific research and optimization on five key aspects:completion methods,reservoir casing sizes,completion string configurations,packer type selection,and sand pocket designs.Building upon these optimizations,comprehensive calculations were further performed for drilling and completion investments,drilling and completion cycles,and economic evaluation indicators.In cases where economic evaluation indicators fail to meet expectations,increasing single-well production is suggested as a means to resolve potential conflicts between enhancing well construction quality and meeting economic evaluations.