Hi Mohd

These rocks have different composition

Yes different composition

Calibration method for pyrolysis analysis parameters S1 and S2 of clastic rocks

Author: Teng Yuming, Ding Lianhua

Auditor: Chen Dongjing

Shengli Petroleum Administration Geological Recording Company

August 197th

Calibration method for pyrolysis analysis parameters S1 and S2 of clastic rocks

I. Foreword

The S1 and S2 values measured by the pyrolysis of clastic reservoir rock samples are residual content, which cannot directly show the original oil and gas state of the reservoir. There are many influencing factors, including hydrocarbon loss caused by changes in formation temperature and pressure, hydrocarbon loss caused by drilling fluid erosion, and hydrocarbon loss caused by sample collection and preservation. All these factors directly affect the reservoir evaluation effect, so it must be corrected to evaluate the reservoir. In the practice of geochemical logging in the past decade, according to the analysis and conclusion of different rock samples in the clastic rock reservoir of hundreds of wells, a pyrolytic hydrocarbon loss correction method suitable for the sand and mud analysis profile of Shengli Oilfield has been established, and good results have been achieved. The following is a brief introduction.

II. Analysis of loss factors of pyrolysis analysis parameters S1 and S2 of clastic rocks

For rock pyrolyzers with three peak analysis, the direct analysis parameters are S0, S1 and S2. S0 is a C1-C7 gaseous hydrocarbon obtained at a temperature of 90°C. The reservoir content is very small (except the gas layer), and the sample analysis value is very small to zero. The loss factor will not be discussed here. Focus on the loss factors of S1 and S2 values.

The S1 value represents the amount of liquid hydrocarbons between C8 and C33 obtained by the thermal evaporation of the rock sample at a temperature interval of 90°C and-300°C. The S2 value represents the content of heavy hydrocarbons and colloidal asphalt above C33 in the temperature range of 300°C and 600°C. According to the physical properties of petroleum hydrocarbons, the S1 value is mainly liquid light hydrocarbons, which is very unstable and volatile. Therefore, the pyrolysis analysis S1 value cannot represent the original hydrocarbon content of the rock sample, but a residue. The S2 value is not equal to the absolute amount of recombinant fractions and colloidal asphalt of rock samples, but is still a residue. The factors causing the loss of pyrolysis analysis parameters S1 and S2 value can be summarized in the following aspects:

1. The change of formation temperature and pressure and the flushing of rock samples by drilling fluid cause some hydrocarbon losses.

After the local layer was drilled, the temperature and pressure of the formation changed. The gas dissolved in crude oil escaped from the reservoir and took away some liquids, mainly oil and water, reducing the hydrocarbon content of the rock sample analysis values S1 and S2. When the rock sample returns from the bottom of the well along the wellbore to the ground, the contact between the oily rock sample and the drilling fluid is washed away, causing part of the crude oil in the rock sample to be washed away by mud, thus reducing the hydrocarbon content of the rock sample analysis values S1 and S2.

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2. The sample analysis values S1 and S2 adopted by different logging methods are different. The rock samples obtained by the three logging methods of core logging well, wall centering and debris logging are at the same level and depth. The S1 and S2 values obtained through analysis are quite different....