推靠式旋转导向工具造斜率预测方法

A method for predicting the build-up rate of"push-the-bit"rotary steering tool

推靠式旋转导向系统可显著地提高钻速、改善井眼条件并大幅度提高井眼延伸长度,代表着现代导向钻井技术的发展方向。为了准确预测和评估推靠式旋转导向工具的造斜率,在常规导向钻具组合力学模型的基础上,考虑推靠块与井壁的相互作用、钻头与地层的相互作用、导向钻具结构等因素影响,建立了推靠式旋转导向工具钻进轨迹预测模型以及“极限造斜率”和“折算造斜率”的计算方法,从“杠杆效应”“钟摆效应”“推靠效应”的角度揭示了造斜率的影响机理,分析了推靠力、钻压、井斜角、钻头与地层各向异性等参数对造斜率的影响规律。研究结果表明:①导向钻具的造斜率是各种效应的综合结果,其中“推靠效应”起主导作用,杠杆效应和钟摆效应起到次要作用;②对于推靠式旋转导向钻具,随着钻压增大,杠杆效应所占比例增大,推靠效应所占比例减小,造斜率减小;③造斜率与钻具结构参数、推靠力、钻头性能、钻进参数等因素密切相关。结论认为,该研究成果可以为推靠式旋转导向工具造斜率预测以及钻具结构优化设计提供重要的理论基础。

Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order to accurately predict and evaluate the build-up rate of push-the-bit rotary steering tool,this paper establishes the drilling trajectory prediction model and the calculation methods of"limit build-up rate"and"corrected build-up rate"for push-the-bit rotary steering tool by comprehensively considering the interaction between biasing unit and sidewall and between bit and formation,the structure of steering bottom hole assembly(BHA)and other influential factors based on the mechanical model of the conventional steering BHA.Then,the influence mechanisms on the build-up rate are revealed from the aspects of"leverage effect","pendulum effect"and"thrust effect".Finally,the influence laws of thrust force,weight on bit(WOB),hole deviation angle,bit and formation anisotropy on the build-up rate are analyzed.And the following research results are obtained.First,the build-up rate of steering BHA is the comprehensive result of various effects,among which"thrust effect"plays a dominant role and"leverage effect"and"pendulum effect"play a secondary role.Second,as for the push-the-bit rotary steering BHA,the proportion of"leverage effect"increases,the proportion of"thrust effect"decreases and the build-up rate declines with the increase of WOB.Third,the build-up rate is in a close relationship with BHA structural parameters,thrust force,bit properties and drilling parameters.In conclusion,the research results can provide an important theoretical basis for the prediction of build-up rate of"push-thebit"rotary steering tool and the structural optimization design of BHA.