Proper fluid and proppant placement are crucial to successful propped fracture stimulation. Numerous completion diagnostic technologies are available to characterize the placement of the treatment. Until recently, characterization of fracturing fluid cleanup could only be simulated in the laboratory and anecdotally monitored in the field. A technique utilizing a family of unique, environmentally friendly, fracturing fluid compatible, chemical tracers has now been developed for quantifying segment-by-segment recovery for individual fracturing treatments and stage-by-stage recovery for multi-stage fracturing treatments. Case histories demonstrate that individual, chemically-differentiated and/or proppant-differentiated, fracturing treatment segments and/or individual fracturing treatment stages are often not being effectively recovered. It has also been demonstrated that the chemical make-up and/or the proppant scheduling of these individual fracturing fluid segments may not only be detrimentally affecting their incremental cleanup but ultimately the production contribution from the corresponding portions of the fractured reservoir. The validation of improvements in fracturing fluid cleanup and production enhancement resulting at least in part from changes in the chemistry of the fracturing fluids and/or changes in proppant scheduling are demonstrated using the tracer technology. Introduction Chemical Frac Tracers In an effort to bolster the level of understanding regarding the dynamics of hydraulic fracture placement and subsequent fluid flowback/cleanup, the technology of chemical frac tracers (CFT's) was born. Borrowing from many years of experience with interwell tracing, several families of non-radioactive chemical compounds were identified that could potentially be placed in segmented portions of the frac fluid so as to more directly measure the flowback efficiency of each fluid segment. Armed with this flowback profile data together with the net pressure history of the frac treatment, it was believed that much could potentially be learned both about the dynamics of segmented fluid placement as well as segmented fluid flowback/cleanup. Given the established formation/fracture damage potential for conventional proppant transport fluids, those fluid segments not adequately recovered following the treatment could, in principle, detrimentally affect the effective flow capacity of the fractured interval. Chemical frac tracers were designed to be placed in chemically-differentiated and/or proppant-differentiated fluid segments of the fracturing fluid so as to assess the cleanup of the fracture as a function of segment fluid chemistry and/or fracture geometry. In so doing, it was believed that the sufficiency or insufficiency of addition rates for key frac fluid additives such as polymers, breakers and gel stabilizers could be assessed. It was also believed that the relative cleanup of individual frac treatment stages in a multiple stage completion procedure could be monitored. It was further hoped that inferences could be made from these data regarding lateral placement effectiveness of proppants and vertical communication between zones. Background The detrimental effects of fracture conductivity reduction resulting from incomplete fracturing fluid flowback/cleanup are well documented. Most of these studies have focused on the effects of flowback procedures on postfrac well performance.1–4 Some of the detrimental effects associated with improper flowback procedures include proppant flowback, proppant crushing, and fracture plugging. Despite its inherent effects on well performance, frac fluid flowback/cleanup has been overshadowed in recent years by a preoccupation with proppant flowback and methodologies for preventing flowback.

The optimistic outlook of the petroleum industry, especially with regard to natural gas, has led to a renewed interest in shale gas plays and more specifically to the Haynesville Shale formation. Through the use of post-stimulation completion diagnostics, insights have been obtained that can be utilized to optimize future hydraulic fracturing completions. This paper will illustrate the use of post-stimulation completion diagnostics in identifying trends that are associated with effective completions in the Haynesville Shale. Case histories will be presented which illustrate methods that have increased the overall completion effectiveness in relation to proppant placement, wellbore deliverability, and ultimately increased production performance. A horizontal well database (> 500 wells) was compiled to identify effective completion trends across the Haynesville Shale formation. By employing proppant and fluid-based tracers, hydraulic fracture characteristics, well deliverability, and ultimately production performance were measured to highlight trends that increased overall completion effectiveness. Primary completion results highlighted areas including, but not limited to, effective proppant placement, full lateral production, frac stage length and containment, perforation cluster spacing, wellbore lateral length, and constrained flowback effects. This paper reviews many of the insights that have been developed through this use of post-stimulation completion diagnostics in the Haynesville Shale formation and which have led to increased completion optimization, production enhancements, and field-wide cost reductions.

It is well accepted by the Oil and Gas industry that approximately 30%-40% of perforations or perforation clusters do not contribute to the production of a multi-stage fracturing stimulated well. Diversion is a common method to maximize the wellbore coverage. The objective of this study is to evaluate and maximize the effect of diversion in multi-cluster horizontal well hydraulic fracturing applications using water hammer profile analysis, step down test and microseismic monitoring. In this study, the authors demonstrated integrated approach for the well stimulation efficiency evaluation. A number of methods have been used for analysis: First, step-down tests after each stage have been used to estimate perforations accepting fluid. Second, innovative method of the high frequency surface pressure record analysis was used to detect diversion. Additionally, microseismic monitoring was used as an independent measurement that allows to validate the results. Eight wells were hydraulically fractured with multiple clusters per stage. Each stage is separated either by frac baffles or plugs. Diverter was pumped to promote more uniform wellbore stimulation. Shut- in procedure was implemented after each diverter step. Signatures of water hammer during shut-in are recorded by high frequency pressure gauge and analyzed in real-time using advanced algorithm from speech processing domain. Locations of clusters receiving fluid were calculated and diversion results are qualified. Microseismic measurements in some of the evaluated wells and step down tests are also performed to qualify the diversion process. All of these measurements were done in real-time and utilized to maximize the number of frac propagations, which will have a positive impact on production. This engineering technique allows the operator to make informed real-time decision based on the effectiveness of inter-stage isolation and diversion. Small footprint high frequency pressure monitoring (HFPM) allows the optimization of cost/BOE ratio.

The lessons learned in the Wolfcamp formation from utilizing completion diagnostics have greatly increased productivity over the years. By employing proppant tracers and subsequent spectral gamma ray logging, along with water-based and oil-based chemical tracers and subsequent produced fluid analysis, trends have been observed, and, where appropriate, changes have been made to the wellbore design, landing interval and subsequent frac design. Throughout the changes, completion diagnostics were utilized and referenced to hydraulic fracturing characteristics, drainage patterns, wellbore spacing, geologic identifiers and overall completion effectiveness, as measured by post-stimulation well performance. This paper reviews many of the insights that have been developed through the use of completion diagnostics in the Wolfcamp formation, as revealed by an extensive database of completed wells. These insights have led to completion optimization, improved well architectures, production enhancements and field-wide cost reductions. The lessons learned should prove useful for both established Wolfcamp operators as well as those new to this play.

The development of unconventional resources in North America has led to the implementation of a variety of drilling and hydraulic fracturing techniques. This paper reviews completion diagnostic data from over 50 wells in the Anadarko and Williston Basins that were evaluated by a multidisciplinary team. Production analyses were conducted in conjunction with the diagnostic data to further qualify the effectiveness of different completion practices. Stimulation diagnostics including proppant tracers, microseismic data, and permanently installed fiber optic sensors are available to assist with identifying fracture growth both within and outside of a targeted interval. Wells in this study will utilize proppant tracers for the evaluation of stage coverage and isolation effectiveness. This paper specifically focuses on isolation techniques used during hydraulic fracturing of uncemented multistage horizontal wells, including swellable packers, and single and dual-element hydro-mechanical packers. Stimulation coverage and zonal containment for these isolation techniques were evaluated, and the results demonstrate how different isolation techniques can affect production. This study shows how operating conditions may also affect the integrity of certain isolation techniques, as results for the most effective isolation techniques vary by basin. These operating variations, among others, are examined in this paper as a possible contributing factor for the loss of annular isolation and corresponding production decreases. Isolation techniques are often implemented in drilling and completion programs with insufficient data or field trials. Most of these decisions are made based on perceived cost optimization rather than the overall completion effectiveness and performance of the well. This study is the first of its kind using a macroscopic analysis of completion diagnostics and production data over a large data set for the evaluation of isolation techniques.