What Does a Mudlogging Geologist Do?

The logging interpretation method is the process of taking underground rock with a coring tool and analyzing and researching it to obtain various data during drilling. The core taken is the most intuitive and reliable reflection of underground geological characteristics. First-person information.

Logging interpretation method

Logging geologists can study the lithology, physical properties, electrical properties, and hydrocarbon-bearing properties of the formations encountered through core analysis; master the characteristics of the oil-generating layers and their geochemical indicators; investigate the distribution of paleontology and sedimentary structures, and determine the sedimentary environment; Fault conditions, such as formation dip angle, formation contact relationship, fault location; identify necessary data and data during the development process, check the development effect; provide geological basis for production increase measures.

The specific work of logging interpretation is to first process the collected logging data, obtain the reservoir evaluation parameters, perform qualitative interpretation of the individual logging data, and then combine the logging data, core analysis, oil testing and other data to make a plate. Interpretation and comprehensive analysis and judgment, determine the interpretation conclusion of oil and gas and water layer, and predict the production capacity of oil and gas layer. From the research object, it can be further subdivided into oil-water layer interpretation, gas-water layer interpretation and water-flooded layer interpretation.

The qualitative interpretation of oil, gas and water layers mainly uses a comparative method to distinguish them. In the process of qualitative interpretation, the following comparison methods are mainly used:

Oil-water layer interpretation process:

Collection data processing-application technology and effective parameter optimization-single data interpretation-interpretation chart establishment-comprehensive analysis and judgment-reservoir production capacity prediction

Logging interpretation method application technology and effective parameter optimization

1. Main application technology

Rock core and other physical observation and judgment technology

Gas measurement data interpretation technology

Geochemical analysis and evaluation technology

Fluorescence microscopic image analysis and evaluation technology

Blowout, well surge, well leakage, oil and gas water invasion and drilling fluid oil and gas display interpretation technology

Log interpretation technology

2. Effective parameter optimization

Parameters reflecting effective thickness: core oil-bearing occurrence and thickness, logging interpretation of well sections and corresponding curve characteristics, well wall coring of oil-bearing sandstone wells in deep positions, cuttings containing oil showing well sections, and gas survey abnormality showing well sections.

Parameters that reflect porosity: core analysis porosity and pore type, logging interpretation of porosity, sonic time difference, lithological density, neutron density curve characteristics, geochemical thermal weight loss analysis porosity, nuclear magnetic resonance analysis porosity, core, Cuttings, core lithology, grain size, sortability, roundness, etc., and face images were analyzed using fluorescent images.

Parameters that reflect permeability: core analysis permeability, core, rock cuttings, core lithology, grain size, sortability, roundness, cementation, fillings, fractures and bedding structure development, etc., fluorescence Image analysis of pore clarity, connectivity, logging natural potential, natural gamma, acoustic time difference, microelectrode amplitude difference, well diameter, etc.

Parameters that reflect oiliness: cores, cuttings, and borehole cores to observe oil-bearing characteristics at one time, geochemical analysis of rock hydrocarbon content, gas measurement analysis of total hydrocarbon content and abnormal display curve shapes, blowouts, gushing and other abnormal phenomena and drilling The surface of the liquid tank shows the characteristics, logging resistivity and its curve characteristics.

Parameters that reflect the physical properties (percolation) of crude oil: core, rock cuttings, and coring of the borehole wall to observe oil-bearing characteristics, geochemical analysis of rock hydrocarbon component content, relative content and spectroscopic morphological characteristics, fluorescence image pore oil color And distribution characteristics, relative content of gas analysis components, blowouts, surges, and other abnormal phenomena, as well as display characteristics of the drilling fluid tank pool surface.

Parameters that reflect water content: characteristics of water content in cores and borehole cores, geochemical analysis of relative content of hydrocarbon components and their morphological characteristics, gas analysis analysis of H2, CO2, and CH4 content, and gas anomaly display curve shapes and groups It is divided into relative content, fluorescence image water-containing characteristics, and logging to explain water saturation.

Parameters reflecting formation pressure: drilling fluid density and blowout, well surge and other abnormal phenomena, comprehensive logging d index, index and drilling fluid volume and other parameters.

Due to the complexity of underground geological phenomena, real strata are difficult to obtain directly. Sensory phenomena, curve features, graphic features, image features, macro wellhead anomalies, etc. in logging and logging wellbore collection data can be used to obtain reservoirs. Important information about the parameters.

Interpretation method of single logging data

1. Gas interpretation and comprehensive logging instrument data interpretation technology

Gas measurement is the main method for detecting natural gas in the wellbore, and the comprehensive logging instrument is a supporting technology for gas well drilling.

1) Analysis of influencing factors of gas measurement display

Influence of reservoir and oil and gas characteristics

Reservoir oil and gas content, gas-oil ratio, crude oil properties, permeability, formation pressure, and other characteristics of reservoirs and oil and gas itself are the main influencing factors of gas survey display.

Influence of drilling conditions

A. Influence of drill diameter

When other conditions are constant, the larger the drill diameter, the larger the volume of broken rock, and the more oil and gas content into the drilling fluid.

B. Influence of drilling speed

Under the same geological conditions, the greater the drilling rate, the larger the volume of broken rock per unit time, and the more the oil and gas content into the drilling fluid.

C. Influence of drilling fluid displacement

The larger the displacement, the shorter the staying time of the drilling fluid at the bottom of the well, and the gas entering the drilling fluid through diffusion and percolation methods will be relatively reduced.

D. Influence of drilling fluid density

In general, in order to ensure the normal drilling construction, the pressure of the drilling fluid column must be slightly higher than the formation pressure. Taking the pressure equilibrium point as the boundary point, the difference in the effect of drilling fluid density on gas content is significant. In the under-balanced state, the differential pressure gas will far exceed the broken gas.

E. Influence of drilling fluid viscosity

The high viscosity of the drilling fluid reduces the degassing efficiency of gas logging, which makes the abnormal value of gas logging low, the base value of gas logging will increase to varying degrees, and the upward migration of oil and gas is not obvious.

F, the effect of single root and aftereffect gas

Disadvantages: First, it increases the difficulty of identifying the true and false display of gas measurement, and second, it affects the true value of gas measurement display. Advantages: It can be used as an auxiliary means for judging the oil and gas layer and the degree of oil and gas, and it is also an important reference for real-time detection of gas leak display.

G. Effect of drilling fluid treatment agent

In the current drilling process, a certain amount of drilling fluid treatment agent must be added to the drilling fluid according to different drilling construction requirements. In general, drilling fluid treatment agents will affect gas logging in varying degrees.

2) Method of gas measurement data correction and parameter processing

The correction of gas survey data is a correction of the environmental influence factors during logging, mainly the correction of the influence of different drilling conditions.

Correction of influencing factors of drill diameter

This effect is mainly caused by the difference in the volume of the broken rock. The correction method is to recover according to the proportional relationship of the volume of the broken rock. Generally, a 215mm3A drill bit is used as the standard. At present, only the borehole volume can be corrected. It cannot be ruled out. Impact of Different Bit Types (AB-PDC) on Rock Fragmentation. The influence of the coring bit is the focus of the correction. The correction factor of the rock crushing volume is:

K = V1 / V2 = D12 / D2-d2

The dilution factor is:

K = D12 × Q2 × t2 / [Q1 × t1 × (D2d2)]

In the formula: D1diameter of normal drilling bit; Ddiameter of coring bit; ddiameter of inner cylinder;

t1, t2drilling time during normal drilling and coring; Q1, Q2drilling fluid displacement during normal drilling and coring.

Correction of factors affecting drilling speed

In the current gas measurement data recorded in time, the difference in drilling speed has a greater impact on the gas display value. The key to correction is to establish a standard drilling rate (or drilling time) and return the real-time data to the standard drilling rate To improve the comparability of gas measurement parameters. On the other hand, the method of integration can also reduce the impact of drilling speed on data.

Correction of influencing factors of drilling fluid density

Statistically analyze the correlation between pressure difference and oil and gas reservoir productivity, and establish the relationship curve equation of the effect of drilling fluid density change on gas measurement display.

The drilling fluid density correction formula is:

Qt 0 = a × (1eb × (pd)) + Qt

In the formula: Qtthe measured total hydrocarbon value; Qt 0the total hydrocarbon value under the pressure equilibrium condition; pthe ground pressure coefficient;

ddrilling fluid density; a, bfactor.

Correction of influencing factors of drilling fluid viscosity

Through simulation test methods, correction coefficients for viscosity changes of different drilling fluid systems are established. The correction formula is:

Qjz = (1 + a) × Qt

In the formula: Qjzcorrected gas content value; acorrected coefficient (values according to the following table); Qtmeasured gas measured value.

Correction of influencing factors of wellhead gas evolution

Through on-site sampling tests, a full-hole analysis of wellhead drilling fluid, a full-scale analysis of mud tank drilling fluid, gas measurement and analysis of total hydrocarbons, and composition analysis are performed to establish a wellhead calibration method for detecting total hydrocarbon emission while drilling.

Correction of influencing factors of single root and aftereffect gas

Developed real-time data acquisition software for gas measurement, which converted the parameters recorded in time into the parameters recorded in depth, extracted the collected data in the drilling state, filtered out the data in the cycle, and affected the pipeline delay each time the pump was turned on Processing, to obtain a gas logging continuous data curve similar to the logging curve, also known as "time-deep conversion".

Radon gas measurement parameter processing method

A. Data processing process:

Conversion of data collection format of different instruments-pipeline delay data processing-abnormal data processing-bit diameter influence correction-coring well section correction-duplicate data, empty data deletion-equidistant data extraction-area integration CorrectionRegression processing of all hydrocarbon base valueDivision of display layerDrilling fluid density (pressure difference) correction of gas-producing and oil-producing layers- Correction of wellhead fugitive gas-Data processing and output.

B. Evaluation parameters

Hydrocarbon filling coefficient:

WD = HS / He

In the formula: WD-hydrocarbon filling coefficient; Hs-gas survey display thickness; He-effective reservoir thickness.

Apparent air saturation:

SG = 100 × C /

In the formula: SG formation apparent gas saturation; total porosity.

3) Evaluation of reservoir physical properties using comprehensive logging parameters

Evaluation of the physical properties of the reservoir using the drilling rate method

The drilling time parameters reflect the drillability of the rock. When drilling into different rock formations, the drilling time is different. Under the condition of stable weight-on-bit and speed, the lower the drilling time, the better the rock's drillability, that is, the better the rock's physical properties, the more developed the rock cracks and pores; the higher the drilling time, the worse the rock's drillability. That is, the worse the rock's physical properties, the less developed rock cracks and pores. While drilling, it is inversely proportional to the number of turntables and weight-on-bit.

Since the number of rotary table rotations and weight-on-bit systems implemented in different well projects are different, and the same well is in different well sections, its rotary disk rotations and weight-on-bit parameters also vary, so when the same rock is encountered in different situations The required drill time varies. In order to accurately judge the physical properties of rocks, the influence of these parameters on the drilling time should be eliminated as much as possible to facilitate comparison and analysis according to a unified benchmark. For this reason, the original drilling-time data of comprehensive logging needs to be corrected to the same reference plane. At the same time, for comparison and analysis, the corrected drilling-time is processed to obtain the drilling speed parameters.

Applying dc index method to evaluate reservoir physical properties

The dc index is a comprehensive evaluation parameter reflecting the rock drillability. It is calculated based on the drill-time parameters and the correction of the drill bit diameter, weight-on-bit, drill disk speed, and drilling fluid density.

Application of work index ratio method to identify fracture development

Under the same drilling parameters, the relative size of the drilling time can be used to identify the fracture development section. However, in actual drilling, drilling parameters are changing at any time, and are affected by many factors such as formation lithology, rock strength, bit type, weight on bit, and revolutions during drilling. In many cases, it cannot truly reflect the drillability of the formation. The effective parameters of the cracks were established as a work index model.

Applying rock drillability evaluation parameters to evaluate reservoir physical properties

According to the optimized drilling design, the lithology of a certain horizon in an area should have an optimized drilling condition. Under this condition, a safe and optimal drilling speed will be obtained. That is, when the standard drilling is performed, the lithology is the same. Assuming the drilling conditions are unchanged, the size of the drilling time can reflect the physical properties of the reservoir. When the actual drilling time is> standard drilling, the permeability of the rock hole encountered is poor, and when the actual drilling is <standard drilling, the rock hole encountered is the same. Good permeability.

At present, it is difficult to achieve standard drilling time with different lithology through experimental methods. Therefore, the method of mathematical statistical fitting and regression is practically feasible. First, the samples were screened, and representative sample data was selected for attribute analysis at the time of drilling. Eight major rock types such as mud shale, sandstone, conglomerate, andesite, breccia, and rhyolite were identified as research objects. Correlation analysis with engineering parameters and geological factors to extract the characteristic parameters reflecting the rock's un-drillability "engineering factors", and according to the correlation analysis of the geological factors and engineering parameters, extract the characteristic parameters reflecting the rock's drillability and its physical properties " Geological factors ". The realization of the method takes into account the different dimensions of the weight-on-bit, speed, torque, and vertical pressure parameters, as well as the dependence of engineering parameters and geological factors on lithology and drill bit type. First, these engineering parameters are standardized to eliminate the dimensions. The difference in the contribution weight of each parameter in the statistical model brought by the difference of.