The Finite Element Modeling Of Micro-spherically Focused Log

With the advancement of technology, oil and gas exploration and development needs, it is now possible and necessary to investigate the concrete characteristics of micro-spherical log. Micro-spherically focused logs under resistive and conductive invasion of drilling mud have different characteristics. The cause for this phenomenon is the attraction or rejection of the current by invaded zone and the original formation. The ration of guard-current to main current(that is, downhole equipment and shielding current intensity of main -- Current intensity ratio) changes, thereby affecting the apparent resistivity curve of ups and downs. However, these changes have quantified specific conditions, and entered the zone, formation characteristics and the shape of the curve, not be considered. Only such an impact factor of the study clearly can reservoir evaluation in practical application of the log characteristics, against boreholes, and the formation of micro-invasive with spherical shape Highlights log, the influence of forward modeling studies, facilitate reservoir identification and evaluation of the application.Based on the combination of Li Daqian and others using the finite element simulation focused on the micro-spherical two-dimensional electromagnetic field effects to optimize the focus of the micro-spherical polar plate electrode spacing; Kang and others using finite element program Automatic Generation System (FEPG 3.0) to simulate micro-spherically focused logging in three dimensional electrostatic field on the basis of results, use Ansoft Corporation finite element software Maxwell 2D/3D right micro-spherically focused logging The finite element method is modeling.This paper is divided into six parts to tell the story, first introduced the micro-spherically focused logging history and current situation and the significance of the study is to examine and the content; Secondly, three were part of the electromagnetic field on a simple finite element method and the basic theory; Part IV outlines a Ansoft's Maxwell 2D/3D software operating environment and its operation and use; Part V of micro-spherically focused logging works and finite element simulation results and analysis.In conclusion different model for the micro-spherically focused logs affected. For different models, a micro-spherically focused logging FEM forward modeling, proved that the use of this software is modeling is feasible and effective. This paper discusses the different environment on micro-spherically focused logs in the following conclusions :(1) With the cakes resistivity and rock resistivity contrast to the decrease, micro-spherically focused logs in the high strata of aggression interface "kick" features gradually weakened, become more and more like the non-invasive high resistance to the formation situation; Low profile invasion of borehole and formation resistivity contrast is large (hundreds), the formation interface is "kickback" With decreasing contrast, the curve has become increasingly smooth, the rate has been increasing.(2) formation of high aggression in the stratigraphic thickness of 1m bimodal have begun to emerge, more than 2m layer basically the same shape. the range is getting lower and lower; Low profile curve shape of aggression with the thickness little change, but with the rate of increase in thickness, 3~4m layer thick achieve basic rate, but also the thick layer half of the top curve. Stratigraphic thickness of the change curve-filled, is penetrated with the vertical depth along with the stratigraphic thickness increases that the actual impact of the change curve is penetrated with vertical depth, This is the micro-spherical curve focus is reflected without washing with the status quo Influenced decision.(3) under the conditions of high aggression, with the invasion zone thickness increased, the curve of the interface, the recoil gradually weakened, curve magnitude, gradually close to the high resistivity layer without invasive form of the curve; aggression in the low profile, with the thickness of the invasion zone, installed, the shape of the curve is smooth, then the layer industry trend shows a rush to the non-invasive high resistance level curve would consequence, gradually reduce the amplitude curve. (4) entered with rock resistivity and the resistivity contrast is the line shape shape the decisive factor. Under conditions of high aggression, as long as the invasion zone resistivity than rock, similar curve shape, With the rate of invasive resistivity increases with the increase; Low aggression conditions, with the invasion zone resistivity increases, the rate curve, Originally gradually smoothing the curves show individual.Finite element method for forward modeling software, how to improve the speed of its operations and the value of the border to deal with the need to do further studies; and later to more complex computational models, and improve the accuracy of operation.