The Study On Response Characteristics Of The Array Induction Logging In The Horizontal Wells

With the continuous development of the petroleum exploration technology,the horizontal drilling technique has become an important technique in oil and gas exploration and development,and has been widely used in different types of reservoirs.Horizontal drilling technique,not only brings huge benefit in the development of oil and gas fields,but also has new issues in the engineering technology,such as logging.The log explanation theory in the vertical logging does not apply in the horizontal well.Therefore,by the COMSOL finite-element software,The thesis studies in detail the response characteristics of the array induction in deviated well and horizontal well,researches influences of factors such as the irregular borehole and intrusion,layer interface and intra-layer heterogeneity,and analyses the response mechanism of tool in the layer near the interface,which provides the theoretical basis for the array induction logging interpretation in horizontal Wells.The contents of the research are divided into five parts.In the first part,the development background,advantages,instrument structure parameters and performance indicators of the array induction logging tool HDIL are stated.Deduce the electromagnetic field distribution of the induction log in homogenous formation.Study the measuring principle of the two-coil system and of three-coil system.The second part studies the response characteristics of the array induction in deviated well and horizontal well.Firstly,based on the COMSOL finite-element software,the array induction model is built in the deviated well and horizontal well in three layer formation.The influences of the array induction logging tool are calculated when the layer thickness,the conductivity contrast between surrounding rock and purposes layer and angle is changed respectively.The results show that the response characteristics of the array induction in the horizontal well depends on multiple factors,such as layer thickness,conductivity contrast,subarray spacing and the distance from tool to layer interface.When the layer thickness is greater than the tool resolution,the response in the horizontal is close to that in the vertical well;When the layer thickness is less than the tool resolution,the response in the horizontal well is obviously different from in the vertical well.The peak appears when tool is into or out of the interface.For a given layer thickness,compared with the vertical well,the difference ofthe long subarray is greater than the short subarray.In the deviated well,when the dip angle of the tool is less than 30o,the angle effect on the response is small.When the angle changes from 30oto 80o,from the shortest subarray to the longest subarray,the angle effect increases gradually.The peak appears in the interface as the main receiver from high resistance into low resistance.The third part researches that the key-type hole in horizontal well influence the response of the array induction logging.First of all,based on the COMSOL finite-element software,the key-type hole model in horizontal Wells of three layer formation is created.The influence of the array induction logging tool is calculated,such as the hole size,the conductivity contrast between mud and formation,tool in eccentric situation and the borehole position on the three layers.The results indicate that the factors has great influence on the short sub-array,which include the size of the hole,the conductivity contrast between mud and formation and the tool in eccentric situation.The reading of subarray 5 shows a negative abnormal when the conductivity contrast larger and borehole eccentricity is small or the tool is in less eccentric situation;In the three layer formation,short subarrays are less affected by the change of thickness due to the borehole effect.The value of the long sub-array in horizontal well is affected by the mud is not as serious as in vertical well,compared with no borehole,peak phenomenon weakens at the interface between layers.The fourth part studies that the ellipse-type invasion in horizontal well influence on the array induction logging.First of all,based on the COMSOL finite-element software,the ellipse-type invasion model in horizontal well of the three layer formation is created.The influence of the array induction logging tool is calculated when the invasion size,borehole in eccentric situation,the conductivity contrast in invasion situation and position of the invasion in three layers are changed.The results show that invasion shape increasing in the direction of gravity less affected,and invasion in the direction of the orthogonal gravity change influence.Invasion in eccentric situation,invasion conductivity and mud conductivity mainly impact the short subarray,the conductivity of the target stratum affect each subarray,the conductivity of surrounding rock affect the long subarray;In three layer formation,the reading of subarray one in the target stratum into conductivity,the subarray five in reading is close real conductivity of the surrounding rock,the peak phenomenon of the long subarray at the interface weakens compared with no invasion.The fifth part researches that intra-layer heterogeneity influence on the array induction logging.Firstly,based on the COMSOL finite-element software,the intra-layer heterogeneity model in three layer formation is built.The influence of the array induction logging tool is calculated.The influences include the rhythmicity and interlayer the intra-layer heterogeneity.Results show that,in the rhythmicity formation,short subarray cannot read true formation conductivity when the middle layer is thin.The reading is close to the true conductivity when thicker.The long arrays can determine the location of the interface layer.The magnetic field distribution and the eddy current flow are mapped from different location apart from the transmitter coil in different cross section of the positive rhythm formation.They show the refraction phenomenon between the different conductivity interfaces.Referred to the interlayer,the interlayer thickness great influence on long subarray,the conductivity curve of each subarray in the side of the narrow target stratum gradually are complicated,when moving the interlayer position on one side of the surrounding rock.the peak phenomenon of the long array at the interface between layers is more complex than that in three layer formation,but the each subarray reading are gradually closed to the true conductivity of the purpose layer on the other side.