American Oil and Gas Reporter - July 2015 - 74

SpecialReport: New Products/Technology

The process for selecting rejuvenation candidates includes estimating remaining reserves, assessing current reservoir conditions, characterizing flow from existing fracs, and identifying
untreated or understimulated zones. As illustrated here, combining production logs with reprocessed seismic data and cuttings analysis helps identify the best intervals along the lateral
for restimulation.

The amount of information available around a well has grown
from a few key data points to hundreds of variables related to reservoir geology, field production, overall recovery, decline rates, well
architectures, completion tools and techniques, pumping schedules,
stimulation fluids, and production schemes. Taken together,
these data can generate an almost infinite number of combinations.
An iterative process and advanced analytical tools, including predictive models, are required to help pinpoint the best candidates.
Advanced data mining techniques can provide a look into virtually any play in North America, enabling operators to study key
production drivers. However, datasets involving large well
counts often contain many variables that are not ideally distributed, or have missing values, bad values or other problems. Therefore, it is crucial that the tools and techniques used in data mining be able to flag any potentially compromised data.
In addition, building a single, multiple-source dataset can minimize the risk of information "gaps" and help ensure the most accurate and reliable screening. By using state-of-the-art data gathering and data filtering algorithms and geographic information
system mapping, it is possible to merge data from multiple sources
(both public and private), and then analyze them to determine well
placement, original completion type, and original stimulation treatment details.
These methods can help operators better understand the impact of key well architecture, completion and stimulation parameters, and can enable them to create base lines for reservoir performance that can be used to explore the potential of various rejuvenation techniques within a specific area. Using this base line,
operators can identify wells that have more production to offer,
and that can be rejuvenated effectively and economically.
The comprehensive candidate selection workflow is used to
assess all known attributes and arrive at a ranked list of the "best
candidates." The ranking process is based on analyzing three categories of important factors: reservoir, completions, and wellbore
mechanics.

Diagnostics And Treatment
Following candidate selection, additional diagnostic analyses
of each well can uncover unique production challenges and delineate issues that might preclude a specific type of rejuvenation
treatment or render it uneconomic. A comprehensive examination of all formation evaluation data helps quantify the remain-

74 THE AMERICAN OIL & GAS REPORTER

ing reserves in a well, in addition to aiding in understanding reservoir conditions. If formation evaluation data are scarce or unclear,
it may be necessary to gather new logging data prior to investing additional money into rejuvenation treatments.
Almost every wellbore will require a thorough cleanup prior to any rejuvenation attempt. With some wells, the clean-out
is sufficient to temporarily boost production to desired recovery
levels with no additional rejuvenation.
A detailed review of the original completion and stimulation
design can help create a diagnostic profile of the existing fractures and help identify any areas that may have been left untreated or understimulated. The completion type and details on the
stimulation treatment are analyzed to evaluate their effectiveness
and to determine the optimum recompletion and restimulation program. Evaluating casing and verifying well integrity helps determine the most effective isolation method for restimulation.
As noted, production can be restored to desired levels with a
well clean-out program, chemical treatment, and/or artificial lift
technology in some cases. However, if additional rejuvenation
measures are required, options include:
* Repairing or replacing a substandard completion;
* Enlarging fracture geometry and enhancing reservoir contact;
* Restimulating underperforming intervals with more suitable fluids and proppants;
* Extending well life by introducing flow assurance additives;
* Increasing conductivity in inadequately propped portions
of fractures;
* Restoring and maintaining fracture conductivity lost because
of proppant embedment, cyclic stress, proppant degradation, gel
damage, or plugging from organic or inorganic depositions;
* Stimulating untreated or undertreated zones for greater reservoir exposure; and
* Recompleting the well to provide more access to the reservoir.
The rejuvenation program should be built on a process that
weighs the technical feasibility and risk against the cost of intervention. Because of the importance of managing flowback in optimizing flow rates and production, it is also important to consider how the well will be put back on production after the treatment. Restimulating a well increases inflow performance, so by
installing artificial lift systems after a well is restimulated, the
well can be drawn down to further enhance production and increase estimated ultimate recovery.
Optimum production and reliable operations are ensured by
Heat Map

Map data  2014 Google Imagery  2014 TerraMetrics

Selecting the best candidates for rejuvenation is not as simple
as identifying underperforming wells. In fact, the best rejuvenation candidates often are the best performers in a field. Heat
maps help reveal the highest-producing areas of a play (red).
Wells located within these "hot spots" may represent prime rejuvenation candidates. Underperforming wells located within
these areas also can be among the best candidates.

American Oil and Gas Reporter - July 2015

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