麻黄山区块深井钻井液技术

Drilling Fluid Technology for Deep Wells in Mahuangshan Block

宁深1井是部署在麻黄山区块的一口区域深探井,该井设计井深5820m,采用三级井身结构。根据地质特征,认为该井钻井液主要技术难点为二开裸眼段长达3130m,井眼尺寸大,且地层破碎、倾角大,易发生垮塌及井漏,钻井液维护困难;山西组、太原组煤层较为发育,井壁容易失稳;预计井底温度高达185℃,高温对钻井液流变性、滤失量控制影响大。根据各开次的需求,室内形成配套钻井液体系,一开选用钾铵基聚合物钻井液体系;二开采用聚合物防塌及聚磺防塌钻井液体系;三开采用聚磺非渗透防塌钻井液体系。采用"多元协同"防塌技术解决井壁失稳,确保二开电测、下套管一次性成功,二开井径扩大率为13%,低于设计要求的20%。受二开套管事故的影响,三开施工井下情况复杂,及时调整钻井液性能,确保了该井的顺利完钻(完钻井深4756m)。在三开下部含多套煤层情况下,井径扩大率只有15.76%。采用非渗透处理剂进行随钻堵漏,可有效降低钻井液漏失。

The well Ningshen 1 is a deep exploratory well with 5820m depth and three-order well profile, which deployed in Mahuangshan block.According to geologic characteristics,the major difficulty of drilling fluid is as follows： the fractured and high inclination formation is easy to collapse and loss,meanwhile it is dif- ficult to maintain drilling fluid performance for the second spud with 3130m big size open hole;the devel- oped coal layers in Shanxi group and Taiyuan group show wellbore instabilization;the expected bottom temper- ature is high up to 185~C affecting the rheological property and filter loss greatly.Based on the need of every spud ,matching drilling fluid system is formed in the laboratory ,drilling fluid system of potassium-ammonium polymer is selected for the first spud,drilling fluid system of polymer anti-sloughing and polysulfonate anti-sloughing is selected for the second spud,and drilling fluid system of polysulfonate non-permeability anti-sloughing is selected for the third spud.Multi-coordination anti-sloughing technology is used for solving the problem of wellbore instability,and the second spud electrical logging and casing running will be successful once.Enlarged rate of hole diameter during the second spud is 13%,which is lower 20% than that designed. Under the effect of the casing accident during the second spud ,the third spud operation is complex ,so the performance of drilling fluid should be adjusted in time to make sure of the well completion with 4756m.The enlarged rate of hole diameter during the third spud in lower segments is 15.76% in the situation of many sets of coal beds.The non-permeable treating chemical is applied for sealing in drilling ,which may make the loss circulation of the drilling fluid drop.