Application of interval seismic velocities for predrill pore. The same phenomenon is also reflected in the pore pressure plots of fig. Misleading prediction of geopressures for a particular area are linked to. Changes in pore pressure can be recognized on regular formation evaluation tools such as sonic, resistivity, porosity, and density logs. Although the analysis of the results of this test is not finalized yet, it seems clear that the effect on the 4d vsp data is rather small. Methods to determine pore pressure equivalent depth methods.
Pore pressure calculation methods dug insight user manual. Detection methods traditionally use drilling parameters and well log information. Match seismic velocity to sonic logs, check shots and geological tops when. Siregar2, radig wisnu y2, setiabundi djaelani2, and benny a. Methodology used to derive the overburden gradient key parameter of terzaghi equation different techniques can be used according to well data available. Seismic pore pressure prediction methods of evaluating abnormal pore pressures are separated in two categories, prediction methods and detection methods.
Improvement in pore pressure prediction resolution using cggs high densit y anisotropic velocity. Pore pressure prediction and modeling using seismic velocities. Postdrill analysis of pore pressure and fracture gradient. This paper depicts a new methodology to analyze pore pressure based on both, the normal compaction theory of sediments and the way that normal behavior. This paper depicts a new methodology to analyze pore pressure based on the normal compaction theory of sediments. Pore pressure prediction is the ability to create numerical formulas that. New approaches for predicting pore pressure from well logs were also presented by 8, where empirical methods for abnormal pore pressure prediction were adopted to provide a much. Porepressure estimation ahead of the bit while drilling. Determination of pore pressure from sonic log iranian journal of. New methodology for pore pressure prediction using well logs. In most drilling projects, this prediction is updated during drilling using logging while drilling lwd logs, mud weights, cuttings, and drilling events such as kicks and mud losses. Pore pressure prediction is the ability to create numerical formulas that mimic the subsurface pressure profile. Pore pressure can be calculated via a variety of methods from either well logs or seismic velocities. Eatons equation eatons method equations for ppp are described in figure 3, and can be made from either velocity slowness or resistivity measurements, in the well or from data volumes.
It is time now that pore pressure prediction formed an integral part of prospect evaluation and well planning. Abnormal pore pressure leads to drilling complexity and well control issues because of reduced. Origin of overpressure and pore pressure prediction in the. Misleading prediction of pore pressure is linked to. Quad operations real time well delivery 1 predrill modeling drill a well utilizing all available offset data, including any and all petrophysical logs, seismic surfaces and geological data to establish an accurate. A 12level vsp tool was installed in one well, while a neighboring injector well was shot down in order to generate a pore pressure drop. Bulletin of earth sciences of thailand department of geology. Pore pressure prediction in shales undergoing compaction, including both mechanical and chemical processes, is customarily related to the mechanism referred to. To optimize drilling decisions and well planning in abnormal pressured areas, it is essential to carry out pore pressure predictions before. Abnormal pore pressure indicators from the well logs, mud logs, and wellbore instability events are identified and analyzed to interpret abnormal pore pressures for guiding realtime drilling decisions. Pdf pore pressures in most deep sedimentary formations are not hydrostatic. Determination of pore pressure using divergences research india.
However, shale pressures cannot be measured directly but are, at best, an educated guess made by correlations that use other information, such as well logs, mud weights and seismic data. Pdf new methodology for pore pressure prediction using well. Case study of onshore nigerdelta sedimentary basin. During well planning, pore pressure experts examine offset data such as basin models, results from leakoff tests lots, engineering and geological reports, seismic data, well logs, and mud weights. The model is one of the most widely utilized methods for predicting formation pressure using well logs in the industry 4. Pore pressure gradient can be determined either from well logs resistivity log and sonic log or from. Hottman and johnson 1965 conducted the first study on the pore pressure prediction using shale properties derived from well log data. The industry practice to determine pore pressure or overpressure from well logs depends on important assumptions. Recent investigations into the effects of pressure on shale porosity suggest that the relationship is more complex than previously thought. However, without establishing the geological groundwork for these mathematical equations, results can be misleading. The prediction methods normally use data obtained from seismic surveys, offset well logs and well history.
Accurate pore pressure prediction in hpht well reduces risk. The pore pressure prediction module is utilised to estimate the effective stress. The pore pressure prediction is the most important process in the design of drilling wells. New methodology for pore pressure prediction using well. Correcting densitysonic logs for total organic carbon to. Pdf estimation of pore pressure and fracture gradient in. Pore pressure prediction porosity stress mechanics. The pore pressure detection using the loggingwhiledrilling, measurementwhiledrilling, and mud logging data is also implemented and evaluated. Sep 14, 2016 pore pressure prediction using geolog. Predrill pore pressure prediction is essential for safe and efficient drilling, and is a key element in the riskreducing toolbox when designing a well. In this way, any deviation in the measured properties from the normal trend line was.
Origin of overpressure and pore pressure prediction in the baram delta province, brunei mark tingay1, richard hillis1,2, richard swarbrick3, chris morley4, and razak damit5. Pore pressure prediction using offset well logs american institute. Optimizing the mud weight program and planned equivalent circulating density ecd was important to minimize wellbore instability in the 9 7. In the shallower section pore pressure computed from inversion almost follows the postdrill curve. Pore pressure modeling has proven and direct implications in oil and gas exploration and development. Application of interval seismic velocities for predrill. A theoretical analysis and case study from an offshore basin, north sea 2 the total overlying rock column, leading to anomalously high formation pressures. Pore pressure prediction from well logs and seismic data resulted in the development of four equations that may be used for the prediction of geopressure from well logs and drilling data. The implementation of a pore pressure and fracture. Two models were used each for predicting pore pressure and the corresponding fracture pressure using well log and drilling data. Integrated approach to pore pressure and fracture pressure.
The subsurface pore pressure buildup partitions are. Pore pressure prediction from well logs and seismic data. Pore pressure calculation methods dug insight 4 user. Development of an appropriate model for predicting pore. Resistivity, sonic, and density logs can be used to construct synthetic seismograms which, in turn, can be used to calibrate and refine seismic profiles. Our work with seismic interval velocities shows that the. It was found that pore pressure prediction cube was normally compacted, or close to normally compacted.
These pore pressure updates, however, use logs from already drilled section of the well and cannot accurately predict ahead of. Pore pressure is the pressure exerted by the fluids within a rocks pore space. Since most well design is based on pressure and temperature models, a wrong prediction can incur either a costly well or a hazardous situation, depending whether the model had over or under predicted the pressures. Shale lithology in niger delta is massive and characterized by high pore pressure. Overburden stress can be easily obtained from bulk density logs, while effective stress can be correlated to well log data, such as resistivity, sonic travel timevelocity, bulk density and drilling parameters e.
Pore pressure prediction pore pressure predictions and transformations that make use of seismic velocity measurements have a huge impact on drilling safety and the economics of drilling design and well construction. Basically the model correlates pore pressure to well log data such as sonic velocity, interval travel time or resistivity. Ugwu and others published pore pressure prediction using offset well logs. Pore pressure predictions for an onshore niger delta area were made using offset well logs. Pore pressure estimation what can we learn from 4d. This work discuss the impact of these key parameters in the pore pressure prognosis. Integrated approach to pore pressure and fracture pressure prediction using well logs. Ozkale thesis corrections6 connecting repositories. Aade05ntce12 five things your pore pressure analyst wont. Enhanced velocitybased porepressure prediction using.
Eatons equation eatons method equations for ppp are described in figure 3, and can be made from either velocity slowness or resistivity measurements, in the well. The pore pressure gradient indicator used is the sonic log from. To obtain this goal, the formation pore pressure is estimated from well logging data by applying eatons prediction method with some. Pdf pore pressure prediction using offset well logs. Pore pressure prediction and modeling using welllogging data in. Develop 3d models for prediction of subsurface pore pressures away from well control. Indepth 3d velocity model left and pore pressure prediction right in equivalent mud weight using the seismic velocities for the 50mi2 area. During the drilling two types of pressures can be predicted which are, 1 reservoir pressure and 2 shale pore pressure paul et al. Methods and complications in determining pore pressures are discussed below. Pore pressure evaluation from well logging and drilling. A pore pressure analysis is premised upon predicting the pressure in shale.
The gradient is called ppg or pore pressure gradient. Pore pressure calculation in a hydraulicallyconnected formation is introduced. Pore pressure estimation is important for both exploration and drilling projects. Rock properties velocityimpedancesvpvs change with. Figure 2 shows sonic travel time varying with measured pressure synthetic seismograms. Shale sections are best for analysis of logs for abnormal pore pressure. Pore pressure prediction using seismic velocity modeling. Besides drilling a well, the only way to predict potential hazards like overpressured subsurface zones is through the use of seismic surveys. A python package for pore pressure prediction using well log data and seismic velocity data. Enhanced velocity based pore pressure prediction using.
Pressure mpa well x 500 pore pressure rises over 20 mpa in 100 m from 12. Overpressure prediction using acoustic logging petrowiki. Seismic pore pressure prediction at the halten terrace in. Crains petrophysical handbook overburden and pore pressure. They use this information and corrected dexponent analysis to model the pore pressures likely to be encountered along the proposed wellbore. In addition, using costeffective methods of pore pressure prediction, which give extensive and continuous range.
Predrill pore pressure profiles along planned well trajectories. Pore pressure prediction methods so far, different methods have been proposed on pore pressure prediction. Equations are given for use with resistivity plots, conductivity plots, sonic traveltime plots, and corrected d exponent plots. Pore pressure evaluation and prediction was undertaken in malcolm field, offshore niger delta, nigeria using wireline log data. Although the analysis of the results of this test is not finalized yet, it seems clear that the effect on the 4d vsp data is. Selecting only the purest shales minimizes the effects of mineral variation, multiple phases, fluid composition, and fluid distribution. Pdf pore pressure gradient prediction using well logs. If no measured formation pressures exist, the mud weight hydrostatic pressure can be taken as the upper limit for the pore pressure. Pore pressure models derived from the integration and careful calibration of.
While additional study is necessary, the results todate suggest that it may be necessary to reconsider or revise the well log methods currently used in pore pressure and exhumation analysis see geological applications of acoustic logging. In extreme circumstances a gas kick can become a blowout with much more disastrous consequences up to and including the loss of the well. One assumption is that the shale pore pressure is the same as pore pressure in sandrich nearby formation e. Because of their low permeabilities, shales do not equilibrate pressure with the mud column in the well bore. Most of these methods are empirical approaches that use data from logs, seismic profiles and porosity determinations. Look ahead well porepressure prediction using full. Pore pressure prediction the pore pressure prediction methods have been developed in the recent decades and many of them are based on the effective stress principle. The conventional approach is to use the normally pressured shale section to derive this nct, then apply it to the overpressured shale section to determine the pore pressure. An estimation of pore pressure can be obtained from seismic velocity as well as from well logs. In some places, an empirical relation can be established to predict pore pressure from well logs.
Postdrill pore pressure analysis of the studied well using pore pressure module, geo suite of software. Look ahead well pore pressure prediction using fwi 4 5 it is evident that the inversion velocity is matching well with the vsp velocity. This study investigated the cause of identified zones of overpressure in some selected wells in a field in the niger delta sedimentary basin. The theory of the bowers and tau methods are presented along with a discussion on the. Qo pressure analysts work with our client teams to develop a predrill pore pressure and fracture gradient model for the well. Multiple scenarios with pore pressure confidence margins. The best pressure to use is the actual, measured, extrapolated shut in pressure for the zone and well to be fractured.
Using interval velocity volume to estimate pre drill porepressure. Velocity determination for pore pressure prediction cseg. These logs show the effects of pore pressure because of the relationship between compaction, porosity, density. Since the quality of any pore pressure analysis can be no. On the well logs the overpressures in arthit field exhibited anomalously increasing transit time and decreasing resistivity in shale intervals with volume of shale more than 80%. On the norwegian continental shelf, pore pressure prediction commonly relies on traditional 1d offset well analysis, whereas velocity data from seismic surveys are often not considered. Pore pressure prediction also influences the decision of casing strings placement. Pdf new methodology for pore pressure prediction using.
Pore pressure prediction reduce uncertainty in pore pressure estimations. However, a number of different compaction trends can be. Lesson 7 pore pressure prediction contents porosity shale compaction equivalent depth method ratio method drilling rate dcexponent moores technique combs method 2 pore pressure prediction methods most pore pressure prediction techniques rely on measured or inferred porosity. Seismic driven pore pressure prediction joanne wang. Pore pressure determinations from measured direct tests mdt at one well confirm the predictive capability of our approach. Perform stochastic analysis of pore pressure models to.
Accurate pore pressure prediction in hpht well reduces. Seismic survey 2d, 3d, 4d, multicomponent pore pressure prediction technology. This method first assumes that there is a depth section over which the pore pressure is hydrostatic, and the sediments are normally compacted because of the systematic increase in effective stress with depth. Mdt as green dots, lot as solid and hollow violet squares from studied well and offset wells, kill mw as solid and hollow red triangles from studied and offset wells. One example of analysis using a trend line is the equivalent depth method illustrated in fig. However, without establishing the geological groundwork for these mathemat. During the exploration phase, a prediction of pore pressure can be used to evaluate exploration risk factors including the migration of formation fluids and seal integrity. The implementation of a pore pressure and fracture gradient prediction model for the north sea central judy and jade fields.
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