The post entitled Reservoir Development’s 2007 Restimulation Survey - Part I summarized the responses to the first three survey questions, and those responses suggested the productivity increase following restimulation is highly variable with about 1/3 of the respondents reporting essentially no increase in production following restimulation and about 1/3 of the respondents reporting greater than 100% increase in production following restimulation. The results from Question 3 offered some insight as to why results are so variable, that is, when “Intuition” is the 2nd leading method for selecting restimulation candidates over all other available diagnostic techniques, shouldn’t variability be expected? Intuition certainly isn’t quantitative: intuition can’t quantify existing stimulation effectiveness, and intuition can’t quantitatively predict the production increase following restimulation. However, several diagnostic techniques can quantify stimulation effectiveness and allow production increase following restimulation to be predicted, which means not wasting money on wells that will not benefit from restimulation.
Continuing the survey discussion, the results of questions 4, 5, 6, and 7 are as follows.
“In wells which are restimulated, what problem(s) was identified for remediation (select all that apply)?”
Fig. 2 shows that the most commonly treated problems, as indicated by 56% of the respondents, are “Bypassed pay” and “Short effective fracture half-length.” It’s also interesting that 2 respondents honestly admitted that they didn’t know the problem being remediated by restimulation.
Reservoir Development’s technology and services were developed to correctly diagnose problems that can be effectively remediated by restimulation. Not all wells are restimulation candidates, and Reservoir Development’s Refracture-Candidate IDs methodology helps operating companies prevent unnecessary restimulation treatments when incremental reserves don’t justify the expense.
Fig. 2. Problems identified for remediation by restimulation. (Click to enlarge)
“What barriers exist to a successful restimulation program (select all that apply)?”
The most common barriers existing to a successful restimulation program, as indicated by more than 50% of the respondents in Fig. 3, include “Time and manpower-for candidate selection,” “Efficient restimulation diagnostic methods,” “Wellbore condition-open perforations across multiple zones,” and “Risk.”
Reservoir Development’s technology and services address each of the four most common barriers. Reservoir Development provides the manpower and software for candidate selection, efficient diagnostics for problem identification, isolated-layer testing and stimulation to minimize the problems of multiple open perforations, and with Reservoir Development’s diagnostics, the benefit of stimulation can be quantified thereby risk can be evaluated.
Fig. 3. Barriers existing for a successful restimulation program (click to enlarge).
The remaining questions in the survey were generally specific to refracturing/restimulation in wells producing from multiple layers. The intent of the questions was to determine the understanding of the unique problems in identifying, diagnosing, and stimulating (IDs) wells producing from multiple layers, and to estimate the market potential for a technology and service company specializing in restimulation-candidate identification, diagnosis, and stimulation.
“In wells which produce from multiple layers, what percentage of targeted pay zones are bypassed or ineffectively stimulated during the original stimulation?”
Twenty-four percent of the respondents indicated that less than 10% of the targeted pay zones are bypassed and 24% of the respondents indicated that more than 30% of the targeted pay zones are bypassed. Overall, 76% of the respondents indicated that greater than 10% of the targeted pay is bypassed or ineffectively stimulated.
Bypassing greater than 10% of the targeted pay is a significant quantity of gas that is either not being produced or is inefficiently producing. Increasing the recovery of a “typical” well with an estimated ultimate recovery of 1 bcf (billion cubic feet) by 0.1 bcf may not seem significant, but over 1000 wells in a field, it represents another 100 bcf of reserves. Reservoir Development’s research shows that up to 30% of layers targeted for fracturing in wells producing from multiple layers are either bypassed or ineffectively stimulated. Reservoir Development’s technology and services can identify, diagnose, and stimulate (IDs) bypassed layers to increase estimated ultimate recovery in mature wells.
“Limited-entry fracture treatments are often the standard design in multilayer tight-gas wells. What percentage of targeted tight-gas zones are bypassed or ineffectively stimulated using limited-entry fracture treatment designs?
The most common technique for stimulating multiple layers with a single fracture treatment is limited-entry fracturing. Sixty percent of the respondents indicated that greater than 10% of the layers targeted for stimulation are bypassed or ineffectively stimulated by limited-entry fracturing techniques.
Reservoir Development’s research shows that several hundred limited-entry fracture treatments were pumped each week in the United States Rocky Mountain region. Evidence from radioactive tracer studies, microseismic mapping, and production logging strongly suggests that 10% to 30% of the layers targeted with limited-entry fracture treatment designs are bypassed or ineffectively stimulated. Consequently, during the “boom” of 2007, several hundred additional wells were added each week to the thousands of candidates for Reservoir Development’s Restimulation-Candidate IDs methodology.
Presenting Reservoir Development’s 2007 restimulation survey will continue in Part III. Please send comments or suggestions to David.Craig@resdevcorp.com.
In March 2007, Reservoir Development Consulting, LLC completed a restimulation survey of consultants and producers operating primarily in North America and typically within the United States Rocky Mountain region. Thirty-eight email invitations were distributed to 6 consultants and 32 managers or engineers representing both major and independent producing companies. Unlike the Spears & Associates survey, no service company personnel were invited to respond. A total of 18 complete responses were obtained, with one response from an operator in the Canadian Rockies and one international response from an operator in Australia.
The survey was designed such that the first 5 questions mirrored those asked by Spears & Associates more than a decade earlier. Results of the first 3 questions are as follows.
“During 2006, the number of restimulation/refracturing treatments your company performed was?”
Sixty-one percent of the respondents indicated they performed less than 10 restimulation treatments in 2006. Eleven percent indicated 50 to 100 restimulation treatments and 6% indicated more than 100 restimulation treatments. While not all 2007 respondents represented Rocky Mountain operators, the new survey indicates more than “limited” restimulation activity. Based on the survey results, a minimum of 240 restimulation treatments were completed by the respondents during 2006.
Clearly, the number of active restimulation programs remains limited, but the number of restimulation programs has increased over the past decade. Reservoir Development Consulting, through providing technology and manpower for identifying, evaluating, and implementing a restimulation program, hopes to increase restimulation opportunities for operators across North America.
“Following restimulation, how much improvement in production was observed?”
Sixteen respondents reported mixed results for restimulation. Thirty-one (31%) percent reported less than 10% improvement in well production following restimulation. Conversely, 31% reported more than 100% improvement in well production following restimulation. Twenty-five percent reported a production increase between 10% and 50%, and 69% of all respondents reported more than a 10% increase in production following restimulation.
Restimulation programs are not widespread primarily because of the uncertainty in productivity increase. In many cases, infill wells have lower risk with predictable productivity and reserves, so instead of optimizing productivity in existing wellbores and producing bypassed gas, drilling new wells is the preferred method for increasing production. The technology and services offered by Reservoir Development Consulting minimize uncertainty and risk in restimulation programs, which can make the programs cost competitive with infill drilling.
“Restimulation candidates are identified by which of the following (select all that apply)?”
As shown in Fig. 1, and as expected, 61% of the respondents indicated that well production was used to identify restimulation candidates, which is similar to the results obtained in the 1995 survey. What was unexpected was that the second most common method for identifying restimulation candidates was “Intuition.” Intuition was selected by more respondents than selected the high tech methods “Fracture diagnostics,” “Production Logs,” “Production-data (rate-transient) analysis,” and “Pressure-transient testing.”
Reservoir Development’s technology and services combine well production evaluation with state-of-the-art diagnostics in an attempt to improve restimulation success, especially in wells producing from multiple layers.
The discussion of Reservoir Development’s 2007 Restimulation Survey results will be continued in Part II.
In 1995, Advanced Resources International, Inc., began studying the North American restimulation market. One of the first orders of business was to enlist the services of Spears & Associates to complete a restimulation market survey. Two objectives were defined by Spears & Associates for the survey. First, producing and service companies were surveyed about well remediation activities, and second, restimulation activity was to be forecast through the year 2000. Spears conducted “almost 100″ interviews in person or by telephone across the different producing regions of North America. In the United States Rocky Mountain region, a total of 19 interviews wee completed with either managers or engineers from producing companies and with service company representatives.
The responses to five questions from the 1996 survey were particularly enlightening:
“In the last 12 months, how much emphasis has your company placed on remediation or restimulation of wells in this region?”
The survey reports “almost noe” as the current operator focus on restimulation in the Mesaverde formation. Frontier formation restimulation activity was reported as being “limited.”
“On average how much improvement results from this remedial work?”
One Mesaverde formation operator reported a 15% productivity and recovery improvement. Operators in the Frontier formation reported more success with remedial treatments. Production rate increases of 50% to 75% were reported.
“What reservoir or stimulation performance problem were you trying to solve?”
All Mesaverde operators surveyed reported that below expectations well productivity was the problem needing remediation. Frontier operators identified multiple problems, including productivity below expectations and problems during the original stimulation treatment.
“How do you determine if remediation is necessary?”
Only well production data was used to identify restimulation candidates.
“What technical barriers prevent more successful restimulation?”
Respondents producing Mesaverde formations replied that reservoir quality is the only technical barrier. Frontier formation producers identified proper stimulation technique and stimulation fluids as the technology barriers.
Overall, the Spears & Associates, Inc., restimulation market survey results found relatively little interest in restimulation in 1996, and the authors forecast a flat US refrac market of about 470 refracs through the year 2000.
The survey predated the massive refracture market that developed following extremely successful refracturing programs in the DJ Basin of eastern Colorado and in the Barnett Shale in north Texas. DJ Basin refracturing began in 1997, and Barnett shale refracturing begain in 1999. By the end of 2004, more than 1,500 refracs had been pumped in the Codell formation of the DJ Basin, and in the same time frame, more than 350 refracs had been pumped in the Barnett shale. By 2009, several thousand additional refracs have been pumped in the DJ Basin, and some Codell wells have been refraced four times. The current dilemma is when to refrac and not if refracs are necessary.
In 2007, Reservoir Development completed an updated restimulation survey. Several subsequent posts will summarize the results of the 2007 survey.
On March 15, 2005, I attended a SPE special workshop on “Accelerating Technology Acceptance,” and I came away from the workshop with one nugget that I’ve carried with me since. Bill dirks, who was then a vice president for Samson Canada, made a presentation entitled “The 10 BCF/Day Gap–Technology Acceleration Imperatives to Meet US Natural Gas Demand Over the Next Decade.” The key slide from the presentation is shown below.
1,600,000 Restimulation Candidate Wells in North America
Mr. Dirks stated that North America contained in exess of 4,000,000 wellbores, and his conservative estimate was that 40%, or 1,600,000 wellbores, had “bypassed pay or restimulation potential.” 1,600,000 wellbores is a big number and represents hundreds of thousands of barrels of oil and trillions of cubic feet of natural gas.
In a 2003 article entitled “Refracture Works,” the number of unconventional gas wells in low-permeability sands was estimated to be 200,000, and the authors wrote that at least 20% of those, or 40.000 tight gas wells, were restimulation candidates with a potential 12 TCF of incremental reserves recoverable following restimulation.
DrBubba, aka Dr. David P. Craig, in addition to owning Reservoir Development Consulting is also an employee of Halliburton. Consequently, Halliburton requires that DrBubba post the following disclaimer:
The information on this site is mine and does not necessarily represent Halliburton's position, strategy, or opinion.
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