|Title of Invention||
"A NEW MATHEMATICAL REPRESENTATION OF ROCK EVAL HYDROGEN INDEX (HI) VS T MAX PROFILES".
|Abstract||This invention relates to an improved method of petroleum exploration comprising the steps of collecting samples from atleast one source rock from different locations of a petroliferous basin, rock eval analyses to obtain parameters: Hydrogen index HI and Tmax, the relation between the parameters is (HI= I/(a* exp (b* (Tmax -435)+C), where a, b and c are unique for a particualr source rock.|
|Full Text||FIELD OF INVENTION
This invention relates to an improved method of petroleum exploration.
BACKGROUND OF THE INVENTION
In petroliferous Basins, petroleum like material namely hydrocarbons, are first generated in organic rich sedimentary sections, called source rocks, by a process of cooking of the organic matter deposited with the sediments. The generated petroleum like matter, through natural plumbing routes in the earth, reaches petroleum reservoirs from where we exploit the accumulated oil and gas. It is an important function of Organic Geochemists, who are an integral part Petroleum Exploration team, to identify the possible source rock sections in a petroliferous area/basin. Other tasks that follow are to rank the source rocks, if more than one source rocks exist, determine the threshold conditions of temperature.
and time of cooking required to begin hydrocarbon generation and the rates of hydrocarbon generation. This helps the explorationists to first identify the best source rocks and roughly estimate how much petroleum may be found in an area and then target the best areas that are connected to the best source rocks for future exploration. At present rapid pyrolysis studies using a commercial instrument called Rock Eval and kinetic calculations are employed for above tasks. The Rock Eval Pyrolysis provides information about the quantity, type and thermal maturity (extent of cooking undergone) of organic matter in the source rocks. One limitation of the kinetics calculations is that relatively uncooked source rocks that are also representative of the actual cooked source rocks of the basin interior are required. This condition can rarely be fulfilled.
OBJECT OF THE INVENTION
An object of this invention is to propose an improved method of petroleum exploration.
Another object of this invention is to propose an improved method of petroleum exploration which obviates the aforesaid disadvantages.
STATEMENT OF INVENTION
According to this invention there is provided an improved method of petroleum exploration characterized in that the method comprises the steps of collecting samples from atleast one source rock from different locations of a petroliferous basin followed by rock eval analyses to obtain parameters: Hydrogen index HI and Tmax, wherein a rock sample is pyrolyzed in rock eval pyrolyzer to obtain the value of S2 and Tmax, which is Temperature maxima at the top of S2 peak, followed by analysis of the rock sample in carbon determinator at a temperature upto 1300°C in which organic carbon is transformed into carbondioxide (CO2), which is measured by the carbon determinator to obtain total organic carbon (TOC) present in the sample followed by determination of HI and the relation between the parameters HI and Tmax as herein described.
DESCRIPTION OF THE INVENTION
The method of the present invention requires Rock Eval data of samples of one or
more source rocks from different locations of a petroliferous basin. Two parameters:
Hydrogen Index (HI) and Tmax obtained from Rock Eval analyses are required. The Tmax
indicates extent of cooking that a sample's organic matter has already undergone in the
interior of the earth. The HI approximates the quantity of hydrocarbons that can still be
generated from the sample sediment. An uncooked sample will show a low value of the
Tmax and a high value of HI that
represents original hydrocarbon generation potential (Hlo) of the sample. On the other hand, a fully cooked sample will show high value of the Tmax and low value of the HI. Partly cooked samples will have intermediate values for these two parameters.
The method of the present invention uses an equation of HI as a function of Tmax to define organic matter in a particular source rock with respect to its original generation potential hydrocarbon generation and the rates. It may also help to identify the source rocks that have expelled the generated hydrocarbons towards the reservoirs, if more than one source is present in a petroliferous area. The proposed HI-Tmax equation is a below:-
HI= l/(a*exp(b*(Tmax-435)+C), where a,b and c are unique for a particular source rock and wherein HI is calculated as HI=(S2/TOC)* 100.
Given, statistically significant, HI and Tmax data of a particular source rock, the
parameters a,b and c of the above equation can be determined by non
curve fitting procedure. A program in C language for the purpose has also been written.
Given the Hi-Tnax equation constants: a, b and c, for a particular source rock, the original generation potential (HIo) and the rate of transformation of the HIo to hydrocarbons (TR) can be determined by the following two equations:
TR= (HIo*a*exp(b*T»ax-435)))/(HIo*a*exp(b*(T»ax-436))+l) The TR values thus calculated for one or more source rocks at different locations can be used to identify the intense cooking regions in a petroliferous basin. The reservoirs that are connected to such identified intense cooking regions are more likely to be oil/gas bearing.
Thus the proposed equation of HI-Tmax can define a source rock interval in term of its original hydrocarbon generation potential, hydrocarbon generation threshold and rate of hydrocarbon generation. If •ore than one source rock intervals are present in a petroliferous area, then the source rocks can be
ranked in terms of the their hydrocarbon generation potential and hydrocarbons generated. Area of intense hydrocarbon generated within a particular source rock interval can also be delineated.
To determine the HI-Tmax equation parameters, uncooked equivalents of the partially or fully cooked actual source rocks, as required for Meaningful kinetic studies, are not required. The HI-Tmax data of source rock unit, correlatable throughout the basin in the framework of sequence stratigraphy and parasequence boundaries, from different locations, representing different cooking levels but similar depositional environments should be used to maintain homogeneity of organic matter facies in the sample set as far as possible.
1. An improved method of petroleum exploration characterized in that the method comprises the steps of collecting samples from atleast one source rock from different locations of a petroliferous basin followed by rock eval analyses to obtain parameters: Hydrogen index HI and Tmax, wherein a rock sample is pyrolyzed in rock eval pyrolyzer to obtain the value of S2 and Tmax, which is Temperature maxima at the top of S2 peak, followed by analysis of the rock sample in carbon determinator at a temperature upto 1300°C in which organic carbon is transformed into carbondioxide (CO2), which is measured by the carbon determinator to obtain total organic carbon (TOC) present in the sample followed by determination of HI and the relation between the parameters HI and Tmax as herein described.
1. An improved method of petroleum exploration substantially as herein described.
|Indian Patent Application Number||1330/DEL/1999|
|PG Journal Number||12/2008|
|Date of Filing||05-Oct-1999|
|Name of Patentee||OIL & NATURAL GAS CORPORATION LIMITED (KDM INSTITUTE OF PETROLEUM EXPLORATION).|
|Applicant Address||JEEVAN BHARTI, TOWER-II, 124, CONNAUGHT CIRCUS, NEW DELHI-110011, INDIA.|
|PCT International Classification Number||G01V 001/28|
|PCT International Application Number||N/A|
|PCT International Filing date|