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GeoMark Research, Ltd.

9748 Whithorn Drive | Houston, Texas 77095

GeoMark Research, Ltd.

info@geomarkresearch.com

USING TIME LAPSE GEOCHEMISTRY FOR WELL SPACING & ALLOCATION

Overview

Time lapse geochemistry (TLG) and production allocation are not new terms and have been around for decades. Initially developed to help understand fluid contributions in conventional systems, this method is still utilized today in these systems and as part of midstream determinations, but it has also spread into unconventional plays.
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TLG, or production monitoring, performs geochemical analysis in a single well at multiple time periods to determine if the fluid is changing—if so, how and why. In unconventional plays, where horizontal laterals are often targeting stacked source/reservoired horizons, the potential for communication between zones as a result of hydraulic fracturing and field development is high. Where individual fluid compartments are producing co-mingled fluid caused by completion methods, it impacts the production capability and lifetime of wells producing from these ingressing zones. Geochemistry analysis of production fluids readily identifies compartmentalization and flags the potential for communication on specific wells and horizons, either due to development or other geologic factors.
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Production allocation is the term used when quantified amounts of which fluids are contributing to production (for example, 30% zone A and 70% zone B). However, while quantification (to +/- 5%) is relatively straightforward in conventional systems, where end-member, non-mixed fluids and homogeneity can be determined, this is rarely the case in unconventional systems. In these latter plays, definitive produced fluid end-members are absent and the majority of lateral geochemical data available indicates heterogeneity exists—both stratigraphically and laterally. This means any end-member you might define has a potentially unknown geochemical range. Therefore, production allocation in unconventional plays should be approached in a semi-quantitative, qualitative manner; whereby, statistically significant changes are assessed and contribution assignment assumes a significant error in the end points for the calculations.

FAQ

Q.What samples should we collect?

Q. The samples collected to build a production monitoring study will vary depending on your overall project objectives, the petroleum system, the phases available, and the available budget. For most projects, the key sample type to collect is produced oil, because this is what is usually being produced and, therefore, is the most critical to understand. Produced gas and produced water samples are also potentially important to collect, depending on your objectives, as they provide further insight into compartmentalization and co-mingling. However, given how often produced water is re-used, end-member examples of what is being pumped down should also be collected if waters are of interest. Understanding the hydrocarbon potential and richness of target zones from core and cuttings samples is also very useful, but not crucial.

Field Sampling Tips: In unconventional plays, the wells often share very similar names, with only the numeral altered across pads (1H, 2H, 3H, and so forth). Therefore, labeling of your collected samples and ensuring the correct well head is being sampled is absolutely necessary to project integrity. Mis-labeling, poor labeling, or mis-sampling can set your project back before it even reaches the lab, and adds cost and time to resample the well. The same requirement applies to ensuring the dates are correctly noted on the collected samples; otherwise, assessing changes through time are hindered.

Q. Why should I undertake a monitoring study?

A. Geochemical assessment of your produced fluids can quickly determine if production is generating from discrete fluid compartments, or whether communication is occurring across your target horizons. Where communication is occurring, GeoMark’s SMEs can advise as to whether the cause is geologic or due to production activities. Understanding the geochemical separation of oil from production zones and its variation in context aids in determining the most appropriate well spacing to maximize production and remove, or at least understand, variable production across the area—even from a limited dataset.

Contact Us

GeoMark Research, Ltd.
9748 Whithorn Drive | Houston, Texas
77095
281-856-9333
info@geomarkresearch.com

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