Analysis of 3D formation pressure based on logging

Authors: YaNan Sheng ZhiChuan Guan Kai Wei

Publish Date: 2016/07/02

Volume: 7, Issue: 2, Pages: 471-477

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Abstract

A method for constructing regional 3D formation pressure based on logging data was established in this paper It aims to deal with the problem of constructing regional 3D formation pressure in the block which is short of the seismic data or has poor quality of seismic data To begin with logging data and core data of drilled wells were collected Making full use of the fine continuity and accurate resolving capability of logging data we calculated the formation pressure of drilled wells based on the Eaton law In addition based on the concept of digital strata the concept of formation matrix was put forward What is more formation matrix of the aimed layer group was built by making use of the drilled well formation pressure based on the epitaxial transfer algorithm Finally we realized the description of the regional 3D formation pressure To verify the reliability of the method one drilled well formation pressure was derived from the 3D formation pressure It was compared with the pressure interpreted by the logging data The maximum error was less than 5  Finally by using the computer visible language the software of describing 3D formation pressure was developed And it is conductive to drilling engineer to predict formation pressure which can provide the basis for the casing design and the selection of the drilling fluid densityResults of geological study on the Niudong block of Qinghai Oilfield indicated that there were many folds and fault zones in the block which made it difficult to predict the formation pressure The vague understanding of the formation pressure caused many complex situations or drilling risks The conventional simple onedimensional pressure prediction result had been very difficult to meet the needs of drilling engineering Analysis of 3D regional formation pressure should be studied in order to improve the prediction accuracy of the formation pressure There have been many 3D formation pressure prediction methods which include loggingconstrained seismic inversion method onepoint hypothesis and spatial interpolation algorithm Xueguo 2005 Honghai et al 2011 Zhi et al 2013 However these methods are all based on the seismic data If the block is lack of seismic data or the quality of seismic data is poor the calculation accuracy of 3D formation pressure based on seismic data is difficult to guarantee With the development of block we can obtain more and more data of the drilled wells such as logging core data and well history information However the method for constructing the 3D formation pressure based on logging data has yet been put forward In this paper a new method was proposed The spatial distribution of 3D formation pressure can be more clearly understood by this methodThe prediction methods of formation pressure were summarized and classified These methods can be classified into three categories according to the order of drilling time pressure prediction before drilling pressure monitoring while drilling and pressure detection after drilling They can also be divided into three categories based on different sources of data the pressure prediction based on seismic data the pressure monitoring by PWD and pressure detection by using the logging data Since then many pressure calculation models had been established such as Eaton law Eaton 1972 Dutta law Dutta 2002 and Fillippone law Fillippone 1979 The pressure calculation model should be chosen to fit the characteristics of geology in the blockThe formation pressure of drilled wells was calculated by different prediction models Then the calculated results and measured pressures were compared Finally we found that the simple Eaton method was suitable for predicting formation pressure in this blockThe digital formation is a comprehensive research system which is gradually developed with the research of the 3D digital GIS Zhang et al 1997 geological modeling Wu et al 2005 and 3D visualization in drilling operations Victor 1997 In order to realize the scientific management and application of the digital formation this paper put forward the concept of the formation matrixTheory and practice have proved that Catuneanu 2009 in the same geological stratum under the same deposition conditions it should produce the same interpretation results of lithology seismic or logging So the formation pressure of the layer group in the block is correlated In the paper by Zhichuan and Kai 2013 based on the drilled well logging data the epitaxial transfer algorithm was established to calculate the target well formation pressure in the same layer group

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