Estimating Oil and Gas Volumes Using Structure Contour Maps

Topics: Oil reserves, Contour line, Petroleum Pages: 13 (4017 words) Published: October 9, 2010

By using the given structure contour map for the Scope field, the given parameters as well as the assumptions, the Oil and Gas Reserve was calculated and are given below:

Table 1: Gas Reserves estimate
Gas Reserves| |
 | m3| Bft3|
1P| 1.30E+10| 368.1|

Table 2: Oil Reserves estimate
Oil Reserves| |
 | m3| MMbbl|
1P| 2.64E+08| 663.6|
2P| 3.67E+08| 922.6|
3P| 8.44E+08| 2123.3|

The properties of the reservoir can be expected to change due to the effect of heterogeneity which is described as in the results section of this report. A platform and certain vertical and horizontal wells were suggested where the vertical wells were suggested to be drilled in the thick oil column which is at the middle region of the structure contour map as it can achieve great vertical reach of the oil whereas horizontal wells were suggested to be drilled near the oil-water contact at the structure contour map as the oil column is not as thick at that region. The optimum production rate calculated from the assumed field life was found to be 126000 bbl/day. The ratio of vertical to horizontal wells drilled was suggested to be 20:6 but can easily be changed and is completely up to the company. The four wells are suggested to be perforated at the centre of the column as this will reduce if not eradicate the effects of the gas and water coning. Pressure maintenance by water or gas injection may not be needed as the volume of the gas cap is substantial and may be enough to be used as a pressure maintenance mechanism by means of Gas Cap expansion. Due to this and also for the fear of the production of oil being affected by the production of gas, it is suggested that the Gas Cap gas should not be produced along with the oil.

Table of Contents

Estimating oil- and gas-in-place6
Estimating Oil- and Gas-in-place and Oil/Gas Reserves9
Results and Discussion10
Estimated Gas and Oil Reserves (Task 1)10
Expected reservoir heterogeneity within the reservoir (Task 2)10
Preferred platform and well locations (Task 3)11
Preferred perforation intervals in the four wells (Task 4)14
Whether pressure maintenance by water or gas injection will be needed during development? (Task 5) Whether Gas Cap gas is preferred to be produced along with oil? (Task 6)14
Appendix 1: Structure contour map for Scope Field17
Appendix 2: Original Iso-pay maps drawn for 1P gas reserve estimation and 1P, 2P & 3P oil reserve estimation18
Appendix 3: Original calculations made to calculate final volume22
Appendix 4: Assignment question paper25


The degree to which the estimation of oil and gas reserves is accurate depends entirely on the availability, quantity and quality of the available data to be used. The estimation of oil and gas reserves is a completely complex process which involves the integration of geological, geophysical, reservoir and production engineering data. In order to arrive at the most likely reserves, the reserves are estimated by using deterministic and probabilistic methods as there are various uncertainties that are involved in the estimating the reserves. In defining the hydrocarbon, Reserves refers to the quantities of oil and gas which can be commercially recovered from a given date forward whereas Resources are the reserves plus additional oil and gas that cannot be produced due to techno-economic factors. In the different stages of a field exploration and developments there are different reserves estimate methods that are generally used at the respective stages. One of the methods which is generally used from when the field is discovered up to when it is abandoned is the Oil and Gas-In-Place method at surface conditions. As usually only some of the oil and gas-in—place can be recovered, therefore the total oil and gas-in-place must be...
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