Determination of depositional environments

1. A method for determining a depositional environment of a sample of a subterranean environment, comprising:

micronizing the sample;

loading the sample in an x-ray diffraction sample holder;

measuring intensities for a crystallographic plane (CP) 100 peak for quartz and a CP 101 peak for quartz in a diffractogram;

calculating a ratio of the intensities of the CP 100 peak for quartz to the CP 101 peak for quartz; and

identifying a depositional environment for the sample from the ratio, wherein a correlation between the depositional environment and the ratio is determined by petrographic analysis.

2. The method of claim 1 , further comprising obtaining the sample from a core sample.

3. The method of claim 1 , further comprising obtaining the sample from cuttings from a drilling process.

4. The method of claim 1 , further comprising comparing peak intensities for other crystallographic planes to measure effects of sample preparation.

5. The method of claim 1 , further comprising comparing peak intensities for CP 112 peaks for quartz for samples from different depositional environments to measure effects of sample preparation.

6. The method of claim 1 , further comprising comparing peak intensities for CP 211 peaks for quartz for samples from different depositional environments to measure effects of sample preparation.

7. The method of claim 1 , further comprising correlating intensity ratios to depositional environment by:

determining the depositional environment for each of a plurality of samples;

measuring the intensity for the CP 100 peak for quartz and the CP 101 peak for quartz for each of the plurality of samples;

calculate the ratio of the intensity of the CP 100 peak for quartz to the CP 101 peak for quartz for each of the plurality of samples; and

correlate the intensity ratio for each of the plurality of samples to the depositional environment.

8. The method of claim 7 , further comprising determining the depositional environment for each of the plurality of samples through a petrographic analysis.

9. The method of claim 1 , further comprising screening a plurality of samples obtained from cuttings generated during a well drilling for depositional environment.

10. The method of claim 1 , further comprising identifying a reservoir layer based, at least in part, on the depositional environment of the sample.

11. The method of claim 1 , further comprising locating a reservoir based, at least in part, on the depositional environment of the sample.

12. The method of claim 1 , further comprising drilling a wellbore to a reservoir based, at least in part, on the depositional environment of the sample.

13. The method of claim 1 , further comprising performing a seismic analyses of a potential location for a reservoir.

14. The method of claim 13 , further comprising using data from the seismic analyses to locate a site for drilling an exploratory well to collect core samples.

15. A method for determining a placement of a well in a reservoir, comprising:

obtaining a sample of rock from a facies in a wellbore;

grinding the sample to form a powder;

mounting the powder in a sample holder and inserting the sample holder in an x-ray diffraction instrument;

determining an intensity of the peak for a crystallographic plane (CP) 100 of quartz in the sample;

determining the intensity of the peak for a CP 101 of quartz in the sample;

calculating a ratio of the intensities for the CP 100 peak for quartz and the CP 101 peak for quartz;

comparing the ratio to a correlation between ratios and depositional environments;

identifying the depositional environment for the sample; and

determining the placement of the wellbore in the reservoir based, at least in part, on the depositional environment.

16. The method of claim 15 , further comprising drilling an exploratory well to obtain core samples of rock in a subterranean environment.

17. The method of claim 16 , further comprising obtaining the sample of rock from the core sample.

18. The method of claim 15 , further comprising obtaining the sample of rock from cuttings from drilling a wellbore.

19. The method of claim 15 , further comprising correlating intensity ratios to depositional environment by:

determining the depositional environment for each of a plurality of samples;

determining the intensity for the CP 100 peak for quartz and the CP 101 peak for quartz for each of the plurality of samples;

calculating the ratio of the intensity of the CP 100 peak for quartz to the CP 101 peak for quartz for each of the plurality of samples; and

correlating the intensity ratio for each of the plurality of samples to the depositional environment.

20. The method of claim 15 , further comprising:

collecting seismic data on a potential reservoir site; and

determining the placement of the wellbore in the reservoir based, at least in part, on the seismic data.