Hexion
Summer 2009
 
fracline
 
Advancements in PropTrac Fracture Diagnostics

Hexion’s Oilfield Technology Group has experienced great success in determining propped fracture height with PropTracSM. The latest technological advancement is calculating fracture width to provide operators with even more valuable information on downhole conditions.

The PropTrac Fracture Diagnostics Service from Hexion incorporates a non-radioactive tag into the resin coating of proppants. This Smart Proppant™ technology is activated by a logging tool after the proppants have been placed in the fracture. The data received is analyzed to identify the location of the tagged proppant and provide information including fracture height and width.

Fracture Width
This new technology was highlighted earlier this year at an SPE (Society of Petroleum Engineers) fracturing conference in The Woodlands, Texas. SPE technical paper 119545 describes the calculation of propped fracture width along with the testing and field studies that were conducted.

Propped fracture width is calculated using a model which predicts neutron reaction rates as a function of position relative to both the neutron source and detector located in the logging tool. Using the Monte Carlo N-Particle Transport Code, a simulator was developed that generated spectrum data based on well parameters and the assumption of a concentration of tagged proppant at that location. The calculated spectrums can then be compared to a database of measured spectrums from the logging run. Values for both propped height and width are validated when the measured spectrum matches the calculated spectrum. The SPE 119545 paper is available on the SPE web site (www.spe.org) and can be reviewed for a more in-depth description of the process.

The new fracture diagnostics technology used to calculate width was recently introduced and field tested. A well in the Muddy Ridge Field (discussed in the Case Study below) was the first well to successfully use the service to determine propped fracture width.

Case Study
The PropTrac service was run in several well types in two different fields located within the Wind River Basin of Wyoming, US. The first field was the Frenchie Draw, whose primary producing formation is the Fort Union. The Fort Union is made up of a complicated group of sand bodies that vary in thickness, continuity, and reservoir properties. The second field was the Muddy Ridge with targeted production in the Fort Union, Lance, and Meeteetse formations.

The identification of pay zones in these formations is a major challenge. They would most likely not be profitable to complete at all except for the use of artificial lift operations and effective water management. These formations are also naturally fractured. The thicknesses of the completion intervals are also significantly different in any wellbore. The reservoir properties such as bottom-hole pressure, porosity, and permeability vary considerably. Previous methods that have been used in these areas perforated all the sands within a certain frac stage utilizing a “blanket” perforating scheme since there was little data to define pay within the frac stages. Also, correlating sands from wellbore to wellbore is complicated because the sands are discontinuous. More recently, the concept of limiting the perforations in a frac stage was introduced. A maximum of six perforation clusters utilizing limited entry perforation schemes were implemented.

The wells in these fields generally have to be hydraulically fractured to be considered productive. The design and analysis of these fracture treatments can be difficult due to the downhole conditions previously mentioned. Fracturing is frequently unsuccessful due to poor propped geometry and flow capacity. They also routinely fail to connect the discontinuous sand packages found in the field.

Operators have historically used many different fracturing and perforating techniques in these types of fields. After completion of the fracture treatments, two specific questions should be answered. The first question to be answered is if the treatment resulted in sufficient propped fracture height and width to ensure adequate stimulation of all targeted pay sands. The second question should answer if it obtained adequate fracture flow capacity to ensure optimum reservoir drainage. Hexionís fracture diagnostics service was recently used to assist in the completion design and to provide answers to these questions.

Results
A total of eight wells in the Frenchie Draw field and three wells in the Muddy Ridge field were completed using the PropTrac service. After fracturing was completed, the PropTrac logs were analyzed in conjunction with other well information. The knowledge obtained from the PropTrac report led the operator to reduce the number of frac stages performed in their wells. An average of one to two frac stages per well were eliminated, significantly reducing their fracturing costs.

To further test and prove the value of the service, the production results of six wells in the same area of the field were directly compared. Three wells were hydraulically fractured utilizing PropTracís resin coated sand and three were hydraulically fractured using 20/40 Ottawa Sand. The corresponding chart shows that the average IP (Initial Production) of the wells using the resin coated sand with the added tag were 33% higher. The 60-day cumulative production average showed 27% higher production levels for the wells stimulated using the tagged resin coated sand.

As these field applications show, the use of this fracture diagnostics service with its resin coated proppants allows operators to optimize production levels while reducing costs, leading to increased profitability.

Summary
PropTrac offers easier, more accurate, and safer on-site operations during fracturing compared to radioactive tracers. It does not require post job cleanup and disposal of radioactive materials. There are no time limits on post frac logging, so it can be used as “insurance” since logging can be run as often as desired. This unique service has the ability to help calibrate frac models for height and width to improve completion strategies and increase well production.

Hexion has a PropTrac facility located in Oklahoma City, OK that houses the PropTrac equipment and personnel. This innovative technology has helped operators enhance their fracturing designs in both the United States and Canada and we will be commercializing PropTrac outside of North America later this year. Additional information on this fracture diagnostics technology can be found at proptrac-video.com.

 

 
 
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