EP4695500A2 - Fracture impact characterization - Google Patents

Abstract

Infill-to-parent well frac hits or fracture driven interactions occur when infill well fractures intersect with parent well depleted fractures or parent wellbores themselves. As a result, both the parent and infill well production can be negatively impacted. Understanding and mitigating frac hits is crucial for unconventional assets since they can impact many aspects of field development. Frac hits can cause parent well production loss, making it an important consideration when it comes to well spacing-stacking, completion design, and drilling schedules optimization decisions. In cases where parent wells have been knocked offline by frac hits, well interventions are often necessary to restore production. Refracturing of parent wells has been proven to protect them from offset infill frac hits, and also presents a secondary field development opportunity.

Description

FRACTURE IMPACT CHARACTERIZATION

BACKGROUND OF THE INVENTION

[001] Unconventional well fracturing impacts on adjacent wells or frac hits, also known as Frac Driven Interactions ( F DI ), are well-to-well communication events initiated by hydraulic fracturing of an offset well. While some wells show production uplifts after a frac hit, many wells experience production degradation or complete loss of production due to failed casing or plugged up wellbores. This negative parent-child interaction presents challenges to Unconventional Reservoir (UR) operators. As an UR matures with more infill development, the number of frac hit events is set to grow given the increased well density and large completion job sizes. UR fracture hits (FH) characterization, production impact prediction methods and mitigation techniques.

[002] In unconventional plays the initial wells drilled and completed on a lease are referred to as "parent wells". The parent well multistage hydraulic fracturing process creates a fracture system that can result in depletion of the reservoir proximal to the wellbore. The magnitude and extent of depletion depend on the Stimulated Reservoir Volume (SRV) initially created (Raterman, et al. 2018) and Drained Reservoir Volume (DRV) that reflect productive fracture areas, well operating strategy and well interference (Raterman, et al. 2019; Kasumov et al. 2022).

[003] The depletion surrounding parent wells presents a challenge for operators when drilling and completing subsequent infill wells because the hydraulic fractures created by the infill wells can preferentially propagate towards the depleted rock around parents due to reduced pressure/stress. This can result in asymmetrical fracture growth and lower the effectiveness of the infill stimulation treatment (Gala et al. 2018; Manchanda et al. 2018; Zhang et al. 2020). Infill- to-parent well frac hits or fracture driven interactions occur when infill well fractures intersect with parent well depleted fractures or parent wellbores themselves. As a result, both the parent and infill well production can be negatively impacted. The impact of frac hits on parent wells can vary between plays. For instance, the Bakken and Haynesville show more positive frac hits than the Eagle Ford and Wolfcamp (Miler et al. 2016; Lindsay et al. 2018; Liu et aL 2020). Several factors and mechanisms driving frac hits, including parent-child spacing, completion design, parent well depletion, have recently been studied and presented (King et aL 2017; Guo et al. 2018; Gupta et al. 2021).

[004] Understanding and mitigating frac hits is crucial for unconventional assets since they can impact many aspects of field development, as illustrated in Figure 1. Frac hits can cause parent well production loss, making it an important consideration when it comes to well spacing-stacking, completion design, and drilling schedules optimization decisions. In cases where parent wells have been knocked offline by frac hits, well interventions are often necessary to restore production. Refracturing of parent wells has been proven to protect them from offset infill frac hits, and also presents a secondary field development opportunity.

[005] What is needed is an analysis and methodology to mitigate fracturing impacts on adjacent wells. SUMMARY OF THE INVENTION

[006] With over 12 years of development in the Unconvention Reservoir, we have collected a comprehensive dataset of frac hits and built an integrated database that incorporates frac hit timing, pressure responses, water/sand volume changes, short- to long-term production impacts, associated parent/child well completion and geological information. In-depth analysis has been conducted on extensive development across an UR. A new integrated workflow including empirical assessment, Multivariate Analysis (MVA) and mechanistic modeling was developed to identify key trends, study mechanisms and predict frac hit production impacts on parent wells. Various techniques have been explored and pilots tested in an effort to mitigate parent-child FH impacts.

[007] The key frac hit impact drivers are identified as parent-child well distance and configuration, parent well depletion, completion design and geology. The models and workflows leveraged have improved the predictability of frac hit likelihood and their production impacts with mechanistic modeling providing insights to the physical process of a frac hit. Several mitigation techniques have been piloted with refracturing of the parent well, optimizing drill schedules to increase distance between infills and high-rate parents, as well as post-frac cleanouts proving effective in the study area.

[008] The invention provides an in-depth analysis of the impact of frac hits on parent wells specifically in the Unconvention Reservoir formation. By combining frac hit data, as well as introduce a new empirical and an integrated MVA workflow provides insights into key frac hit drivers. Additionally, various mitigation techniques are provided to minimize the negative effects of frac hits on parent wells.

[009] In one embodiment, an unconventional reservoir is developed by building a database of unconventional reservoir properties that includes well properties and fracturing impacts; empirical assessment of the well data; multivariate analysis of the fracturing impacts; predict fracturing impacts based on current fracturing properties; and mitigate fracturing impacts by adjusting well and fracturing parameters.

[010] In another embodiment, a process for mitigating fracturing impacts by building a database of unconventional reservoir properties that includes well properties and fracturing impacts; empirical assessment of the well data; multivariate analysis of the fracturing impacts; predicting fracturing impacts based on current fracturing properties; and mitigating fracturing impacts by adjusting well and fracturing parameters.

[Oil] In one embodiment, a computer processor may be configures to calculate fracturing impacts including a database of unconventional reservoir properties that includes well properties and fracturing impacts; an empirical assessment of the well data; a multivariate analysis of the fracturing impacts; configured to predict fracturing impacts based on current fracturing properties; and mitigating fracturing impacts by adjusting well and fracturing parameters.

[012] Unconventional reservoir properties may be selected from incorporates frac hit timing, pressure responses, water/sand volume changes, short- to long-term production impacts, associated parent/child well completion and geological information. [013] Existing parent wells near a new completion pad may be closely monitored, and their pressure, water, or short- and long-term production impacts may be recorded. Existing parent wells may be evaluated within a distance selected from 5000, 4500, 4000, 3500, 3000, 2500, 2000, 1500, 1000, and less than 1000 feet.

[014] Fracturing impact events may be integrated with other relevant information such as geology, completion, and well schedule.

[015] Empirical analysis may be conducted to identify key trends and drivers of fracturing impacts.

[016] Multivariate analysis may be used to model parameters for prediction of fracturing impacts.

Abbreviations

BHP = Bottomhole pressure, psia

BOE = Barrel of Oil Equivalent

BOEPD = Barrels of Oil Equivalent Per Day

DRV = Drained Reservoir Volume

DAS = Distributed Acoustic Sensing

DH = Downhole

FDI = Fracture Driven Interaction

MVA = Multivariate Analysis

SRV = Stimulated Reservoir Volume

UR = Unconditional Reservoir

BRIEF DESCRIPTION OF DRAWINGS

[017] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. For the purpose of illustration, there is shown in the drawings certain embodiments of the disclosed subject matter. It should be understood, however, that the disclosed subject matter is not limited to the precise embodiments and features shown. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate implementations of systems, methods, and apparatuses consistent with the disclosed subject matter and, together with the description, serve to explain advantages and principles consistent with the disclosed subject matter. A more complete understanding of the present invention and benefits thereof may be acquired by referring to the follow description taken in conjunction with the accompanying drawings.

[018] Figure 1 illustrates frac hit impacts on many parts of UR field development.

[019] Figure 2 (a) is an example of well sticks for parent and infill wells. Figure 2 (b) demonstrates frac hit impacts on production rate, water cut and yield on Al.

[020] Figure 3 (a) Monitoring offset infill fracturing through parent well surface gauges, (b) Parent well surface pressure responses to frac hits. [021] Figure 4 Microseismic, DAS and downhole pressure gauge responses to frac hits, (a) Infill well and vertical monitor well locations, (b) Infill well treatment pressure and far field vertical monitor well downhole gauge pressure responses to frac hits, (c) The overlap of DAS, Microseismic and DH gauge responses when frac hits arrived at the vertical monitor well SI.

[022] Figure 5 Integrated frac hit analysis workflow.

[023] Figure 6 Parent well recovery vs parent-child well distance.

[024] Figure 7 Trend between pre-frac hit parent well production rates and frac hit production impacts.

[025] Figure 8 (a) Trend between infill well completion job size and parent well production impacts, (b) Trend between parent well completion job size and parent well production impacts.

[026] Figure 9 Cross-plot of porosity and frac hit production impacts.

[027] Figure 10 Frac hit negative production impacts relative to strength of FEV seismic attribute.

[028] Figure 11 Tubing pressure observed at a parent well during refracturing at an adjacent offset well.

[029] Figure 12 (a) Fracture propagating into parent well depleted region. The fracture width is larger at parent wellbore locations due to increased net pressure, (b) and (c) The figures depict a map view of fracture growth from the refrac well towards the parent well. The thin blue lines represent the existing hydraulic fracture planes of the parent well as modeled. The thick lines from the refrac well represent newly created fractures that intersect with the parent well fractures.

[030] Figure 13 (a) a representative importance ranking of variables impacting frac hit likelihood. Figure 13 (b) a representative importance ranking of variables impacting frac hit volume magnitude.

[031] Figure 14 illustrates one example of a Frac Hit Database.

[032] Figure 16 is an overview of a Multivariate Analysis Frac Hit Impact Prediction Workflow.

[033] Figure 17 (a) a representation of Multivariate Analysis Results importance ranking of variables impacting frac hit likelihood. Figure 17 (b) a representation of Multivariate Analysis Results importance ranking of variables impacting frac hit volume magnitude

[034] Figure 18 overview of a UR Frac Hit Analysis Tool Developed a platform for frac hit database update, data integration, empirical and multivariate analysis & prediction to improve FH assessment efficiency and consistency

DETAILED DESCRIPTION OF THE INVENTION

[035] Turning now to the detailed description of the preferred arrangement or arrangements of the present invention, it should be understood that the inventive features and concepts may be manifested in other arrangements and that the scope of the invention is not limited to the embodiments described or illustrated. The scope of the invention is intended only to be limited by the scope of the claims that follow.

Frac Hit Detection and Data Collection

Parent well production data

[036] Identifying and building a database with frac hit impacts for every parent well has been a significant effort with over 1700 wells drilled in the UR by ConocoPhillips. This provides an excellent foundation where changes to production rate, water cut, yield and pressures are captured. In the example provided in Figure 2, the parent pad was drilled in 2014 and two offset infill pads were drilled in 2017 and 2019, respectively. The 2017 infill fracturing on the southwest resulted in a positive production response, with increased yield due to re-pressurization and potential contact with undrained rocks through newly created fractures (Liu et al. 2021). Water cut also increased as frac fluid from the infill wells reached the parents. The production uplift in the case was temporary, which is commonly observed with the production eventually returning to pre-frac hit trend after a few months. In contrast, the 2019 infill pad to the northeast had a catastrophic frac hit, which knocked the parent well offline and resulted in the loss of the remaining resources. Catastrophic frac hits can have severe consequences on production and lead to costly well remediation. The short and long-term production impacts can be quantified and used as an important input to our analysis and modeling workflow.

Parent well surface pressure

[037] Parent well surface pressure can also be important data for frac hit analysis. It provides a direct measure of the timing and magnitude of frac hits at the parent well, as shown in Figure 3. The frac hit event timing can typically be correlated to the pumping of a specific completion stage when integrated with evaluation of stress and expected fracture orientation. With this information a frac hit pathway can be inferred between the infill and the parent wellbore (see red arrow in Figure 3a). Collating this information assists in the generation of a map that captures all frac hit events with the extension of this analysis to all stages and parent wells.

[038] An example of high-frequency pressure responses to frac hits at a parent well is shown in Figure 3b. The frac hits are indicated by abrupt pressure increases at a rate higher than the normal pressure buildup from well shut-ins. The multiple spikes reflect frac hits that have occurred from multiple frac stages on an infill well. To characterize frac hits, parameters derived from the pressure response include the rate of pressure increase (intensity), pressure increase magnitude, time-to-response, and volume-to-response, among others. An automated tool has been created to identify these pressure-based parameters and record them in a database.

[039] Since parent well surface pressure is typically acquired as standard, it is widely available across the field and aids an in-depth analysis of pressure data and correlation to production impacts that can provide valuable insights not only to frac hits but also to completion effectiveness, fracture geometry, well interference, and their spatial variation.

Special frac hit diagnostic data [040] Frac hits can also be detected using special hydraulic fracture diagnostic data that are not commonly collected, such as Microseismic, Distributed Acoustic Sensing (DAS), downhole pressure gauges, and tracers. An example is shown in Figure 4 from ConocoPhillips' Unconvention Reservoir SRV pilot published by Raterman et al. in 2018. In this case, a vertical monitor well (SI) was drilled 615 feet away from the infill well P3, and fiber and downhole gauges were installed across different Unconventional Reservoir formations to monitor fracture propagation (Figure 4a). As shown in Figure 4b, all three far field downhole gauges successfully captured the pressure spikes in response to frac hits initiated from P3 Stage 6. At the same time, the DAS data, which is sensitive to strain changes, showed extension (red) and compression (blue) fracturing events, and the microseismic events (purple dots) occurred at the monitor well location during the time frac hits were sustained. This pilot and the integration of different data provides valuable insights to characterize the spatial and temporal extent of frac hits, further improving our understanding of frac hit mechanisms.

Other data

[041] In addition to the data discussed above, other relevant information is also used for frac hit analysis. This includes well spatial configurations, such as distance, overlap, and landing zone; completion data, such as frac job size, zipper situation, fluid type, stage length, and cluster spacing; reservoir properties, such as initial pressure/stress, fluid property, porosity, clay content, and faults; as well as operational data like mud loss and cleanout data.

[042] The following examples of certain embodiments of the invention are given. Each example is provided by way of explanation of the invention, one of many embodiments of the invention, and the following examples should not be read to limit, or define, the scope of the invention.

Example 1 : Frac Hit Analysis Workflow

[043] Figure 5 illustrates the proposed integrated workflow for analyzing frac hits. The workflow involves collecting data on fieldwide frac hit events and their associated production impacts, as well as incorporating other relevant information such as geology, completion, and well schedule. Empirical analysis is then conducted to identify the key trends and drivers of frac hits, followed by the development of mechanistic models for a better understanding of the underlying physics and MVA model for prediction. The insights gained from the analysis enable informed business decisions to be made. Further details will be presented in the following sections.

Example 2: Frac Hit Trend Analysis

[044] key variables and their correlation to frac hits.

Parent-infill well distance

[045] Parent-infill well distance is one of the strongest drivers of frac hits. As the distance between a parent well and an infill well decreases, the risk and severity of production loss caused by frac hits at the parent well increases. This trend is shown in Figure 6. Additionally, in a multiwell pad, the parent well that is closest to the infills typically receives the largest frac hits. However, beyond ~3000 feet in this Unconventional Reservoir, there are rarely any frac hit responses observed at parent wells. This trend indicates tighter well spacing can result in higher frac hit impacts.

Parent well depletion

[046] As discussed earlier, hydraulic fractures preferentially propagate towards depleted areas, which can potentially enhance asymmetric fracture growth and lead to more severe frac hits. The production rate of a parent well prior to a frac hit is used as a proxy for its depletion in this study. The production impact of a frac hit increases if a well is hit at a high rate, as shown in Figure 7. While the depletion level may not significantly impact the likelihood of frac hits, a high-rate well can experience more production volume loss if it is affected by frac hits. For this reason, operators often optimize their drilling schedules to avoid fracturing too close to parent wells with strong production to reduce the risk.

Completion

[047] Many completion design parameters, such as job size, stage length, fluid type, zipper, and sequencing, can be related to frac hits since they can influence the fracture length and complexity. Among them, job size has been found to have the biggest impact where we observe that larger job sizes typically result in higher production impacts as shown in Figure 8. The reasons are larger infill job sizes can create longer fractures which increase the likelihood of hitting parent wells, while larger parent well job sizes increase fracture intensity and depletion around parent wells thus increasing the likelihood of connection by newly induced fractures from an infill. Given the strong trends observed, operators should consider the potential impacts of frac hits when they optimize their completion designs. Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. It is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims while the description, abstract and drawings are not to be used to limit the scope of the invention. The invention is specifically intended to be as broad as the claims below and their equivalents.

Geological/Geophysical properties

[048] Several reservoir properties were incorporated into the analysis including porosity, permeability, clay content and geomechanical properties such as Young's Modulus among others. Geomechanical properties and their proxies such as clay content or porosity were the primary geological variables impacting the magnitude of a frac hit. The relationship is not highly correlative. Figure 9 shows a cross-plot of porosity and frac hit impacts, with no clear trend observed.

[049] Within the UR formations faults can be observed, however typically within ConocoPhillips' acreage these are limited and frequently of sub-seismic resolution. To aid identification of structural discontinuities on 3D seismic, we use a fault enhanced volume (FEV) that highlights trace-by-trace discontinuities, with stronger features typically correlating with the presence of faults and/or dip changes. An evaluation was subsequently carried out to evaluate frac hit occurrence and impact relative to the presence and magnitude of these FEV features. While frac hits occur regardless of their presence, there is a subtle correlation between the magnitude of a frac hit and the strength of the seismic feature when intersected along a wellbore, with an increased median negative production impact where stronger features exist (Figure 10). This avenue of inquiry was further pursued with a case study that included integration of microseismic and cross-well strain from fiber, with results so far remaining inconclusive.

Refrac Frac Hits

[050] It had been hypothesized that refracturing parent wells would result in minimal frac hits to offset parent wells, because the pressure is likely to be dissipated into the depleted regions around refrac well(s). However, this study showed that refracturing depleted parent wells induces frac hits to nearby parent wells comparable in magnitude to new infill wells. An example is shown in Figure 11 when observing tubing pressure of a parent well during refracturing of a single well, where each frac stage resulted in a pressure interaction at the parent wellbore. This indicates that depletion at the refractured well did not lower the pressure interaction likely due to pre-existing fractures between the parent wells created during the initial completion of the wells. The magnitude of the pressure event and the time-to-response from the refractured wells were similar to those from the infill wells. In addition, catastrophic frac hits caused by refracturing have been observed and this is taken into account when selecting the number and location of wells for refracturing.

Example 3: Frac Hit Mechanistic Model

[051] Fracture propagation within a multi-well system is dependent on completion design and reservoir properties. For the stimulation of infill wells adjacent to existing wells, the dominant drivers of fracture creation are parent well depletion and existing fracture planes. In this study, fracture propagation in a depleted reservoir has been modeled to understand the interaction of parent well depletion and a pre-existing failure plane and their impact on fracture growth at an infill well. Fracture modeling as shown in Figure 12 may be performed on Schlumberger's Kinetix® Stimulation Software Suite, ResFrac®, Baker Hughes' JewelSuite™ Reservoir Stimulation (ResStim) with MFrac™ Suite, Halliburton's GOHFER® Fracture Modeling Software, Austin GeoTech's STAF Software with Multi-Frac 3D, Carbo Ceramics FRACPRO, at Fracturing Fluid Characterization Facility (FFCF) at the University of Oklahoma, Norman, Matlab, or a team of reservoir scientist may develop their own proprietary software if needed.

[052] Simulation results show the creation of asymmetric fractures with the longer wing growing into the depleted rock (Figure 12a). As the fracture approaches the depleted region increased fracture net pressure (fracture pressure minus the closure stress) results in an increase to fracture width at the most depleted location of the wellbore. In other words, existing depleted fractures can be dilated due to the increased net pressure and enable the proppants at existing fractures to mobilize as the stimulation fluid flows towards the parent wellbore. However, existing proppant pack in parent well fractures need to be agitated to form a slurry before flowing through the perforation holes of the wellbore. In many cases, the parent wellbore appears to be plugged off by solids after only a few frac hit events near the toe of the well. Calculations have shown that the mobilized sand slurry due to the recorded frac hits are not sufficient to fill up the wellbore volume. Thus, it is suspected that the frac hit-induced pressure surge at the parent wellbore picks up wellbore debris and plugs off the parent wellbore at sections with reduced flow area due to debris, scale, etc.

[053] The simulation work also reveals the morphology of the fractures from infill wells interacting with existing failure planes which emulate the existing hydraulic fractures from the parent wellbore (Figure 12 b and c). Under the expected fluid efficiency, hydraulic fractures from the infill wells in the same zone reach the tip of fractures from parent wells within 10 minutes of pumping time. This short duration is repeatedly seen in field operations. However, in many other cases, it takes much longer before a frac hit event is observed at the parent wells. Therefore, it is recommended to use time-to-response or volume-to-response only to qualitatively suggest the relative distance of hydraulic fractures from the parent wells. When time-to-response or volume- to-response is of low magnitude, it indicates that the front of fractures from the parent well is close to the infill well location and vice versa. However, the modeling results do not exclude the possibility that the infill well fractures completely miss the parent well fractures due to stress orientation complexity or uneven fracture growth among perforation clusters.

Example 4: Multivariate Analysis (MV A) and Modeling

[054] An effective implementation of MVA yields applicable data driven models trained on relevant data. The MVA process couples feature selection with a data driven model which allows simultaneous data and model evaluation.

[055] In this study, tree based MVA was used to generate models that predict the implications of future frac hits by effectively ranking features related to geology, completion, well configuration and operating strategy. Specifically, two types of frac hit models were developed and used in conjunction: the likelihood model based on bootstrap forest, and the magnitude model based on boosted trees.

[056] The likelihood model is trained to perform the classification task of predicting the occurrence of a frac hit given a set of features. To clarify, the model outputs a score between 0 and 1, which is used as analog for the likelihood of a frac hit occurring. The response variable is composed of l's for detected fracs hit and 0's for no frac hits. A simple rounding function converts the model response (0 to 1) into classification (0 or 1). The model performance can be evaluated using the test data and model classification response: the model has a true positive rate (correct detection of a frac hit) of 87% and a true negative rate (correct detection of no frac hit) of 86%. The model is highly sensitive to key variables such as parent to infill overlap and distance.

[057] The magnitude model is trained as a regression model which estimates the production volume impact of frac hits. The model learns from the magnitude of past recorded frac hits and lists the key factors. The volume impacts from frac hit are highly dependent on geological parameters such as Poisson ratio and clay content, parent well cumulative volume produced, and infill completion design (Figure 13). Tests show that the magnitude model achieves a correlation coefficient of 0.9 and a normalized root mean squared error of 15%. [058] The MVA model is continuously updated and fine-tuned to improve predictability as new data and understanding become available. This enables the team to quantitatively assess the risk of frac hits and influence project development and field optimization.

Example 5: Frac Hit Mitigation Techniques

[059] Developed a platform for frac hit database update, data integration, empirical and multivariate analysis & prediction to improve FH assessment efficiency and consistency. Various mitigation techniques were tested in the field to minimize production loss impacts caused by frac hits. However, some of these techniques were found to be ineffective. For example:

[060] Pumping water into the parent (PIP) well for re-pressurization. This technique can lead to production degradation of parent wells due to elevated water cuts coupled with the impact of frac hits.

[061] Using far field diverting agents in the infill well fracture treatments. This technique showed mixed results.

[062] On the other hand, there are several proven effective frac hit mitigation techniques, which include:

[063] Refracturing parent wells: Refracturing can dramatically increase the pressure of parent wells and prevent them from experiencing frac hits. Additionally, it can tap into undrained resources and create significant production uplift. However, not all parent wells can be refractured due to economic or well integrity reasons, and refracturing can cause frac hits to offset parents resulting in loss of production that should be accounted for during candidate selection.

[064] Optimize drilling schedules: schedules can be optimized to avoid fracturing too close to high-rate parent wells. This strategy reduces the risk of losing production, however, it can lead to deferral of high-value projects, and is challenging to implement as well density increases.

[065] Post frac hit cleanout: when a frac hit is sustained at the parent well the majority of the lost base production can be restored after removing the solids/obstruction. However, the cost of cleanout can be expensive and depending on the remaining resources, may be uneconomic.

[066] Shutting in parent wells to build up pressure and stress: this technique can provide certain protections to parent wells; however, it results in production deferment and shut-in parents can still experience severe frac hits.

[067] Overall, effective mitigation techniques can help us reduce the negative impacts of frac hits and optimize their production. However, careful evaluation and consideration of the pros and cons are necessary before implementing these techniques.

[068] Frac hits are an important industry challenge that can impact unconventional asset development. The increasing trend of frac hits is expected to continue as more infill wells are drilled and completed.

[069] A rich frac hit data set was built by collating and integrating frac hit events, production impacts, pressure, completion, geology and special frac diagnostic data. [070] The key drivers of frac hits were identified, including parent-infill well distance (spacing), parent well depletion, parent-infill well overlap, and completion design.

[071] Weaker correlations between geological/geophysical properties and frac hits were observed. Further investigations are needed.

[072] MVA and mechanistic modeling proved to be useful in understanding physics and predicting the occurrence and production impacts of frac hits.

[073] Refracturing a parent well can protect its base production from offset frac hits, but it can also induce frac hits similar to those from the stimulation of new wells.

[074] Refracturing, schedule optimization and post-frac hit cleanout are effective techniques to mitigate production loss. However, their pros and cons should be evaluated before implementation.

[075] While the present disclosure has been described with reference to various implementations, it will be understood that these implementations are illustrative and that the scope of the present disclosure is not limited to them. Many variations, modifications, additions, and improvements are possible. More generally, embodiments in accordance with the present disclosure have been described in the context of particular implementations. Functionality may be separated or combined in blocks differently in various embodiments of the disclosure or described with different terminology. These and other variations, modifications, additions, and improvements may fall within the scope of the disclosure as defined in the claims that follow.

REFERENCES

[076] In closing, it should be noted that the discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. Each of the references below is incorporated in their entirety for all purposes.

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Claims

Claims

1. A method to develop an unconventional reservoir comprising: build a database of unconventional reservoir properties that includes well properties and fracturing impacts; empirical assessment of the well data; multivariate analysis of the fracturing impacts; predict fracturing impacts based on current fracturing properties; and mitigate fracturing impacts by adjusting well and fracturing parameters.

2. A process for mitigating fracturing impacts comprising: build a database of unconventional reservoir properties that includes well properties and fracturing impacts; empirical assessment of the well data; multivariate analysis of the fracturing impacts; predict fracturing impacts based on current fracturing properties; and mitigate fracturing impacts by adjusting well and fracturing parameters.

3. A computer processor configured to calculate fracturing impacts comprising: a database of unconventional reservoir properties that includes well properties and fracturing impacts; an empirical assessment of the well data; a multivariate analysis of the fracturing impacts; configured to predict fracturing impacts based on current fracturing properties; and mitigating fracturing impacts by adjusting well and fracturing parameters.

4. Any one of claims 1-3, comprising unconventional reservoir properties selected from incorporates frac hit timing, pressure responses, water/sand volume changes, short- to long-term production impacts, associated parent/child well completion and geological information.

5. Any one of claims 1-4, wherein existing parent wells near a new completion pad are closely monitored, and their pressure, water, and short- and long-term production impacts are recorded

6. Any one of claims 1-5, wherein existing parent wells are evaluated within a distance selected from 5000, 4500, 4000, 3500, 3000, 2500, 2000, 1500, 1000, and less than 1000 feet.

7. Any one of claims 1-6, wherein fracturing impact events are integrated with other relevant information such as geology, completion, and well schedule..

8. Any one of claims 1-7, wherein empirical analysis is conducted to identify key trends and drivers of fracturing impacts.

9. Any one of claims l-8„ wherein a multivariate analysis is used to model parameters for prediction of fracturing impacts.