Lease Boundaries Research Articles

Detection of violations of open-pit mining lease boundaries using Sentinel-2 MSI data in the case of Lao Cai and Yen Bai provinces of North Vietnam

Illegal mining, including the violation of lease boundaries during the extraction of mineral deposits in Vietnam, has witnessed a significant surge in recent years, leading to substantial environmental degradation. Due to the remote locations of mining areas in relation to settlements, the detection of illegal mining activities using conventional methods poses considerable challenges. This study presents a methodology for identifying lease boundary violations in open-pit mining of mineral deposits by utilizing high-resolution satellite images from the Sentinel-2 MSI system. The proposed methodology involves overlaying Sentinel-2 MSI radar-acquired satellite images to identify disparities between approved lease boundaries and actual boundaries of mining areas. The research focuses on the mineral-rich provinces of Lao Cai and Yen Bai in North Vietnam. The findings of this research rhold great potential for effectively monitoring and promptly detecting violations of mining lease boundaries.

Indirect impacts of commercial gold mining on adjacent ecosystems

Mining is important for economic development in many tropical countries, but mining can have serious impacts on biodiversity, both directly through operations at extraction sites, and indirectly via wider social-economic development. However, mitigation efforts by large-scale mining operators focus almost exclusively on extraction sites. We provide a rare assessment of mining impacts on vegetation structure and biodiversity with increasing distance from three commercial gold mines of varying ages in Tanzania (0 years, 8 years, and 19 years since establishment).We show that mining is associated with impacts that manifest largely outside operational lease boundaries. At the two older mine sites, aboveground carbon and tree stem density are significantly higher within lease boundaries compared to outside, while there is no such effect at the new site. Further, tree stem density, aboveground carbon, and tree and butterfly species richness all decrease with increasing distance from extraction sites, with these effects again increasing with mine age. Frugivorous bird species richness is lower outside older mines, while abundance declines in frugivorous and granivorous birds are associated with declines in tree stem density, which may have implications for forest regeneration.These impacts result from new and expanding settlements around mining concessions between 2000 and 2019 and associated demand for timber and fuelwood. We recommend rigorous, integrated impact assessments and conservation planning in mining landscapes, to pre-empt the development of settlements and secondary industries around mining sites and so balance outcomes across the mining sector, natural resource-based and other livelihoods, and conservation agendas.

Machine-Learning Approach Optimizes Well Spacing

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 201698, “Finding a Trend Out of Chaos: A Machine-Learning Approach for Well-Spacing Optimization,” by Zheren Ma, Ehsan Davani, SPE, and Xiaodan Ma, SPE, Quantum Reservoir Impact, et al., prepared for the 2020 SPE Annual Technical Conference and Exhibition, originally scheduled to be held in Denver, Colorado, 5–7 October. The paper has not been peer reviewed. Data-driven decisions powered by machine-learning (ML) methods are increasing in popularity when optimizing field development in unconventional reservoirs. However, because well performance is affected by many factors, the challenge is to uncover trends within all the noise. By leveraging basin-level knowledge captured by big data sculpting, integrating private and public data with the use of uncertainty quantification, a process the authors describe as augmented artificial intelligence (AI) can provide quick, science-based answers for well spacing and fracturing optimization and can assess the full potential of an asset in unconventional reservoirs. A case study in the Midland Basin is detailed in the complete paper. Introduction Augmented AI is a process wherein ML and human expertise are coupled to improve solutions. The augmented AI work flow (Fig. 1) starts with data sculpting, which includes information retrieval; data cleaning and standardization; and smart, deep, and systematic data quality control (QC). Feature engineering generates all relevant parameters entering the ML model. More than 50 features have been generated for this work and categorized. The final step is to perform model tuning and ensemble, evaluating model robustness and generating model explanation and uncertainty quantification. Geology The complete paper provides a detailed geological background of the Permian Basin and its Wolfcamp unconventional layer, an organic-rich shale formation with tight reservoir properties. To find a solution for the multidimensional well-spacing problem in the Permian Basin, multiple sources and types of data were gathered using publicly available sources. The detailed geological attributes, including structure, petrophysics, geochemistry, basin-level features, and cultural information (such as counties or lease boundaries) have been combined in an integrated database to extract and generate features for the ML algorithm. Most attributes are available either in a limited number of wells, mostly vertical, or through the low number of available cored wells across the basin. Therefore, a significant amount of data imputation has been processed with mapping exercises using geostatistical modeling techniques. The mapping process augmented the ML attribute-generation step because these features were distributed in both vertical and lateral dimensions. All horizontal wells within the area of interest across the Permian Basin have been resampled with the logged and mapped information. The geological features also are reengineered into multiple indices to reduce the number of labeled features to include in the ML process. This feature-reduction process also has helped in ranking and selecting the most-important parameters relevant to the well-spacing problem. Here, a key attribute called the shale-oil index was introduced, which is generated for the ML-driven process and is used in understanding the level of contribution of geological sweet spots to well-spacing optimization. In addition, the initial well, reservoir, or laboratory data, including logs, have been normalized before mapping and modeling to eliminate potential bias. This study has focused on Wolfcamp layers; however, both geological and engineering attribute generation work flows used for this practical ML methodology to find optimization solutions for common problems are highly applicable to other unconventional layers, such as Bone Spring or Spraberry.

Drivers, pressures, and state responses to inform long-term oil sands wetland monitoring program objectives

Boreal peatlands provide numerous ecosystem services ranging from carbon sequestration to the provisioning of habitat for species integral to Indigenous communities. In the Oil Sands Region of Alberta, Canada, human development related to oil and gas extraction occurs in a wetland-dominated landscape. Wetland monitoring programs can determine the extent to which development impacts wetlands, but existing monitoring programs focus on characterizing biodiversity across the region and on compliance and regulatory monitoring that assumes impacts from oil sands development do not extend past lease boundaries. This is unlikely to be true since some impacts, such as particulate deposition, can extend over large areas contingent on local weather and topography. To inform the development of a new regional wetland monitoring program to assess the cumulative effects of oil sands development on wetlands, we synthesized information on the scope of wetland research across the Oil Sands Region, including the anthropogenic stressors that impact wetlands and the wetland characteristics sensitive to different disturbances. We developed a conceptual model linking human development with wetland ecology in the region to make explicit the relationships among oil sands development stressors and different components of wetland ecosystems. By highlighting testable relationships, this conceptual model can be used as a collection of hypotheses to identify knowledge gaps and to guide future research priorities. relationships among We found that the majority of studies are short-term (77% were ≤ 5 years) and are conducted over a limited spatial extent (82% were sub-regional). Studies of reclaimed wetlands were relatively common (18% of all tests); disproportionate to the occurrence of this wetland type. Results from these studies likely cannot be extrapolated to other wetlands in the region. Nevertheless, the impacts of tailings contaminants, wetland reclamation activities, and surface water chemistry are well-represented in the literature. Research on other types of land disturbance is lacking. A coordinated, regional monitoring program is needed to gain a complete understanding of the direct and indirect impacts of human development in the region and to address remaining knowledge gaps.

Study of permissible dynamic load on high-pressure gas pipe laying site in connection with blasting operations during open-pit mining

The paper presents the results of a study of permissible dynamic load on high-pressure gas pipe laying site of the II category located within the mining lease boundaries, in connection with carrying out blasting operations at the open-pit mine of JSC Sukholozhsktsement. The procedure of IM UrB RAS for calculating the permissible distances from the technological explosion in the mine to the protected object (gas pipeline) depending on the explosive weight in the stage, coefficient of soil conditions and permissible velocity of seismic vibrations is presented. It is found that depending on the explosion depth in the mine and using corresponding geological data, by changing the weight in the delay stage, it is possible to completely eliminate the negative effect of explosion on pipe laying area. A calculation scheme is also proposed to determine the safe distances to high-pressure gas pipeline depending on the angle of open pit side and blasting depth.

Ground vibration generated by hydraulic rock breakers and its impact on the safety of nearby earthfill dam in a graphite mine

A detailed impact analysis on the effects of non-explosive chemicals and hydraulic rock breakers at a graphite mine in India close to an irrigation dam was carried out in this study. The dam was 70 m from the mining lease boundary. When a single hydraulic rock breaker worked on fractured rock mass, the magnitude of ground vibration recorded at 10 m on the same working bench was 2.37 mm s −1 but when it worked on fresh rock surface the ground vibration at 9 m on the same working bench was 4.67 mm s −1 . Beyond 35 m on the same bench, no ground vibrations were recorded. Ground vibrations generated by three jack hammer drilling machines operating simultaneously on the same working bench were less than 0.5 mm s −1 when measured at 7.2 m distance. The combined effect on the magnitudes of ground vibrations by two hydraulic rock breakers operating simultaneously on the same bench 6 m apart was found to be negligible. The ground vibrations generated by hydraulic rock breakers and other mining activities were found to be lower than required to cause any structural damage or threat to the stability of the dam.

Estimating Stable Measured Values and Detecting Anomalies in Groundwater Geochemistry Time Series Data Across the Athabasca Oil Sands Area, Canada

Regional groundwater monitoring in the Athabasca region of Alberta, Canada, provides information on groundwater quality and geochemical changes over time, including data useful for evaluating potential impacts of industrial activity such as oil sands mining and in situ operations. Data collected from over 5000 wells from the 1950s to 2014, including 161 wells from government’s monitoring network, were used to develop and apply bootstrap techniques for the detection of changes in groundwater geochemistry over time and at specific points in time. Increasing temporal anomalies were identified in Cl, TDS, B, and naphthenic acids in the McMurray formation across 2003 and 2008, while decreasing anomalies were found for SO4. Temporal variance for 15 indicators was quantified for a smooth bootstrap approach to arrive at stable values representative of the most recent samples taken from wells in the study area. Stable values revealed sampling bias in the Devonian, Grand Rapids, Empress, Channel Beverly, and Muriel Lake formations suggesting expansion of sampling may be necessary. Although temporal anomalies were found in the McMurray formation, sampling bias was not identified. The entropy and relative magnitude of time series were evaluated to identify candidate wells for continued observations, which consist of wells with low measurements and low entropy that are near active industry lease boundaries. Temporal anomalies, stable values, and entropy were combined into type-well information to provide plots for visual inspection and interpretation. Stable values are useful for regional mapping, for detecting future changes and trends, and for identifying areas of interest warranting further investigation.

Application of UAV Remote Sensing Technology for Sand Quarry Volumetric Audit and Environmental Impact Assessment: A Case Study Done in Neyvasal Sand Quarry, Cuddalore District, Tamil Nadu—India

Illicit sand quarry in riverbeds will become a menace to the worldwide environment and will lead to changes in the river morphology, physical habitation and ecosystem. The excavation of sand in the riverbed is essential because it helps to maintain the river path and avoid flood inundation during the rainy season. But the excess sand removal only creates a negative impact to the surrounding environment. Hence, effective monitoring and scientific audit method are required to identify the illicit sand quarry. The assessment of excess sand excavated area and volume is a major task for the Economic and Revenue Sector Audit (E&RSA) officials. Also, the volume calculation of sand quarry is a tedious and time-consuming process when using a traditional survey instrument like total station. Integration of unmanned aerial vehicle (UAV) remote sensing (R/S) technology with modern survey instrument like differential global positioning system (DGPS) will reduce the survey time, cost and manpower. In this study, the UAV-based aerial survey and DGPS observation were done in Economic and Revenue Sector Audit (E&RSA), a specified sand quarry site. The acquired UAV aerial images and DGPS points were subsequently used to generate orthomosaic map, digital terrain model (DTM), digital surface model (DSM) and 3D mesh. The UAV-derived outputs have been compared with lease map and revenue records. All the findings related to violations in approved lease boundary, volume and depth were reported to E&RSA to estimate the revenue loss to the government.

Proposed Legislation to Mine Brazil's Indigenous Lands Will Threaten Amazon Forests and Their Valuable Ecosystem Services

A recent proposal to regulate mining within Indigenous Lands (ILs) threatens people and the unique ecosystems of Brazil's Legal Amazon. Here, we show that this new policy could eventually affect more than 863,000 km2 of tropical forests—20% more than under current policies—assuming all known mineral deposits will be developed and impacts of mining on forests extend 70 km from lease boundaries. Not only are these forests home to some of the world's most culturally diverse communities, they also provide at least US $5 billion each year to the global economy, producing food, mitigating carbon emissions, and regulating climate for agriculture and energy production. It is unclear whether new mines within ILs will be required to compensate for their direct and indirect environmental and social impacts but failing to do so will have considerable environmental and social consequences.

Application of Unmanned Aerial Vehicle for Mapping and Modeling of Indian Mines

Geospatial data play a key role in the preparation of mine plan, lease boundary fixing and volume calculation of minerals in the mine. The conventional practice proposed by Indian Bureau of Mine is using differential global positioning system (DGPS), CartoSAT/LISS IV satellite imagery and cadastral maps to provide lease boundary fixing, digital elevation model of mine and rectified cadastral map. Most of the mine has steep terrain which is difficult to survey using DGPS/total station, and it involves human risks. The temporal resolution of the satellite, cost and time required to procure the satellite imagery is high. The increasing affordability of civilian unmanned aerial vehicle (UAV), aerial data acquisition is easy in any topography, time-saving and less cost compared to traditional survey technique like total station and DGPS. The main aim of this paper is to incorporate the proposed workflow to generate the high accurate geospatial data for Indian Mines through the integration of UAV and traditional survey technique. Based on the proposed workflow, UAV-based survey conducted on a iron ore mine and the output geodata were generated. The study discussed UAV geodata-based analytical technique to identify the encroachment, slope unstable area of mine, water disposal route and volume of the stockpile. This helps to reduce the violations in terms of quantity and area, provide a better decision support system to the lease of the mine and increase the revenue of the government.

Long-term studies of lobster abundance at a salmon aquaculture site, eastern Canada

Wild lobster (Homarus americanus) abundance was monitored before, during, and after salmon (Salmo salar) aquaculture production in a bay on Grand Manan Island, New Brunswick, Canada, in an 8-year survey, 2008 to 2015. Diver transects and free-area spot-dives were used to measure the carapace length and determine sex (including berried state) of each lobster encountered both inside (farm) and outside (reference) the lease boundaries. In pairwise comparisons of each sampling date, there was no significant difference between the number of lobsters inside the salmon farming area versus a nearby reference site and no significant difference in the number of berried females inside or out of the farm lease area. Combining data from all lobster surveys (farm and reference sites) indicated an increase over 8 years, similar in slope to the increase of the trap fishery in Lobster Fishing Area (LFA) 38. These results indicate that the fish farm had no obvious impact on lobster density at any point in the salmon production cycle and that inshore lobster abundance followed trends similar to those of the general fishery of LFA 38.

Productivity-Maximized Horizontal-Well Design With Multiple Acute-Angle Transverse Fractures

SummaryHydraulic fractures propagate perpendicular to the horizontal-well axis whenever the drilling direction is parallel to the minimum-principal-stress direction. However, operators frequently drill horizontal wells parallel to lease boundaries, resulting in hydraulic-fracture vertical planes slanted at angles less than 90° from the well axis.The stimulated-rock-volume (SRV) dimensions are defined by fracture height, well length, and fracture length multiplied by the sine of the angle between fracture planes and the horizontal-well axis (fracture angle). The well productivity index (PI) under boundary-dominated flow (BDF) is given by the PI for one fully penetrating fracture multiplied by the number of fractures. An extension of the unified-fracture-design (UFD) approach for rectangular drainage areas enables determination of the unique number of fractures that will maximize well productivity under BDF conditions given the formation permeability, proppant mass, fracture angle, and well spacing. Fracture length and width vary depending on the fracture angle, but the total-propped-fracture volume remains constant.Because the likely reason for drilling at an angle to the minimum-stress direction is to better cover a lease area with north/south and east/west boundaries, the smallest fracture angle will be 45°, corresponding to northwest/southeast or northeast/southwest minimum-stress direction. This results in the need to lengthen fractures by at most 40% to preserve the SRV for a given horizontal-well length and spacing. For the same sufficiently large proppant mass, this will reduce fracture conductivity by the same factor. However, because the flow area has increased, the result will be greater well productivity.This study shows a simple strategy for designing wells to maximize productivity even when not drilled in the minimum-stress direction.

Geotechnical Investigations - A Tool for Deciding Mining Method for Chromite Deposits in Odisha State, India

The Chromite deposits of Sukinda valley, Odisha, India are of strategic importance for the development of ferro-alloy industries. Around 90% of the India’s chromite ore production derived from two important chromite bearing belts, namely the Baula-Nuasahi belt and Sukinda valley ultramafic complex deposit. In terms of rock strength properties, the host rocks and ore body at Baula – Nuasahi chromite belt are hard and compact, with some structural defects such as joints, faults and dykes. After extracting the chromite ore by surface mining up to the economic pit bottom, the remaining reserves were being mined by underground method. In the Sukinda valley chromite deposits, both the wall rocks and ore body are weak, highly weathered. These mines were operated by opencast method. As most of the working mines in Sukinda valley reached their economic pit limit and there is no further scope to extract the ore by opencast mining. Since the chromite ore bodies are having considerable mineable strike length, width, and depth persistence, there is no option except to convert them into underground mines to increase the life of the mines. The chromite ore bodies were proved up to depth of 270m by exploratory drilling. Some major mining companies are planning for underground mining operations, due to constraint of limited space available for waste dumping, working with common lease boundary, slope instability, high volume of stripping ratio. To overcome such problems, the basic step is to conduct the detailed geo-technical investigations to avoid any unexpected consequences during mine development and stoping operations. The geo-technical investigations comprised of geotechnical mapping of existing mined out benches using scan line surveys, geo-technical drilling and logging of cores for the estimation of RQD, structural discontinuities, testing of cores for material properties followed by performing numerical modeling to evolve a suitable stoping method and excavation geometry. The paper deals with the results of the geo-technical investigations carried out for the planning and design of underground mine workings, design of stope parameters based on the geo-mining conditions.

Mining drives extensive deforestation in the Brazilian Amazon

Mining poses significant and potentially underestimated risks to tropical forests worldwide. In Brazil’s Amazon, mining drives deforestation far beyond operational lease boundaries, yet the full extent of these impacts is unknown and thus neglected in environmental licensing. Here we quantify mining-induced deforestation and investigate the aspects of mining operations, which most likely contribute. We find mining significantly increased Amazon forest loss up to 70 km beyond mining lease boundaries, causing 11,670 km2 of deforestation between 2005 and 2015. This extent represents 9% of all Amazon forest loss during this time and 12 times more deforestation than occurred within mining leases alone. Pathways leading to such impacts include mining infrastructure establishment, urban expansion to support a growing workforce, and development of mineral commodity supply chains. Mining-induced deforestation is not unique to Brazil; to mitigate adverse impacts of mining and conserve tropical forests globally, environmental assessments and licensing must considered both on- and off-lease sources of deforestation.

Multi-trophic level response to extreme metal contamination from gold mining in a subarctic lake.

Giant Mine, located in the city of Yellowknife (Northwest Territories, Canada), is a dramatic example of subarctic legacy contamination from mining activities, with remediation costs projected to exceed $1 billion. Operational between 1948 and 2004, gold extraction at Giant Mine released large quantities of arsenic and metals from the roasting of arsenopyrite ore. We examined the long-term ecological effects of roaster emissions on Pocket Lake, a small lake at the edge of the Giant Mine lease boundary, using a spectrum of palaeoenvironmental approaches. A dated sedimentary profile tracked striking increases (approx. 1700%) in arsenic concentrations coeval with the initiation of Giant Mine operations. Large increases in mercury, antimony and lead also occurred. Synchronous changes in biological indicator assemblages from multiple aquatic trophic levels, in both benthic and pelagic habitats, indicate dramatic ecological responses to extreme metal(loid) contamination. At the peak of contamination, all Cladocera, a keystone group of primary consumers, as well as all planktonic diatoms, were functionally lost from the sediment record. No biological recovery has been inferred, despite the fact that the bulk of metal(loid) emissions occurred more than 50 years ago, and the cessation of all ore-roasting activities in Yellowknife in 1999.

Ambient Air Quality Assessment with Particular Reference to Particulates in Western part of Jharia Coalfield, India

India is in the list of fastest growing countries of the world. India's energy needs are also increasing due to population and industrial growth for improving quality of living style. In India, coal is major input infrastructure industries for example Power plants, Steel plants and Cement industries. India’s 52% of primary energy is coal dependent1. 66% of India's power generation depends upon coal production1. Jharia Coalfield (JCF) is falling in the Lower Gondwana Coalfields of India. The area of the JCF is about 450 km2. It is important for the major supply of precious coking coal required for steel plants in India. It is located in Dhanbad district of Jharkhand state of India, The latitude is 23° 39' to 23° 48' N and longitude is 86° 11' to 86° 27' E for the Jharia coalfield. Based on environmental parameters, all the 103 mines of BCCL have been grouped under 17 Clusters. A cluster consists of a group of mines with mine lease boundary lying in close vicinity and includes-Operating mines, Abandoned/ closed mines and proposed projects.The focused study area is in the western part of the Jharia coalfield is named as Cluster XV group of mines of BCCL consists of four mines, Kharkharee Colliery (UG), Dharmaband Colliery (UG), Madhuband Colliery (UG) and Phularitand Colliery (UG) .The present study was carried out with the objective to measure the ambient air quality of the study area with reference to particulate matter (SPM, PM10 & PM2.5). Ambient air monitoring results have shown that the observe air quality were found within the limit prescribed by MoEF / CPCB. It may due to Underground mines as there are pollution causing lesser activities involved in the UG mining process compared to opencast mining. Implementation of Master plan for Jharia coalfields for environmental management has also improve the air quality in the area10,11.

Finding Optimal Hydraulic-Fracture Angles in Productivity-Maximized Shale Well Design

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 170965, “Optimal Hydraulic-Fracture Angle in Productivity-Maximized Shale Well Design,” by Nadav Sorek, SPE, Jose A. Moreno, Ryan Rice, Guofan Luo, and Christine Ehlig-Economides, SPE, Texas A&M University, prepared for the 2014 SPE Annual Technical Conference and Exhibition, Amsterdam, 27–29 October. The paper has not been peer reviewed. In general, hydraulic fractures propagate perpendicular to the horizontal-well axis whenever drilling is parallel to the minimum principal-stress plane. However, operators frequently drill horizontal wells parallel to lease boundaries, resulting in slanted hydraulic-fracture planes at angles less than 90° from the well axis. This study provides a model for the inclined fracture case. It applies and further extends the unified-fracture-design approach for rectangular drainage areas, relating the dimensionless proppant number to the maximum productivity index in pseudosteady-state conditions. Introduction Industry experience suggests that horizontal shale-gas development is enhanced by drilling in the direction parallel to the local minimum principal horizontal stress. Because US mineral leases frequently are rectangular areas with north/south and east/west boundaries, operators often drill parallel to the lease boundaries, prioritizing well saturation over optimum fracture-length propagation. This practice leads to the creation of hydraulic-fracture planes that are slanted at an angle less than 90° with respect to the well axis. Extensive research has investigated the effects of angled fractures on well productivity. Theoretical and empirical data have been used to address the effect of wellbore azimuth on well performance in the Marcellus shale. Results showed that, for each degree a well was suboptimal to minimum horizontal stress, the estimated ultimate recovery decreased by 7.25 Mscf per foot of effective lateral length. Unified-fracture-design methodology indicates the hydraulic- fracturing treatment design that maximizes well productivity for any set of reservoir and proppant properties and a given injected-proppant mass. This methodology introduces the concept of proppant number, which describes the weighted ratio of propped-fracture volume to a square reservoir volume. This study applies and further extends the unified-fracture-design approach to show that, for any given set of reservoir and proppant properties along with a given proppant mass, as long as the created fractures define the same stimulated rock volume, there exists a well direction resulting in maximized well productivity that is not parallel to the minimum-stress direction. First, a correlation is established between the proppant number and the optimum drainage-area aspect ratio. Then, this correlation is used to express what the optimum fracture angle is for a specific proppant number.

Challenges, Opportunities Abound for Artificial Lift

Artificial Lift Artificial lift systems are among the most widely used production technologies in global oil and gas operations. Wells that cannot produce liquids to surface under their own pressure require lift technologies to enable production. Some liquid wells need lift assistance from the beginning, and almost all require it sooner or later. Rod pump, electric submersible pump (ESP), and gas lift technologies are the most common methods of providing artificial lift to these wells. Gas wells also require artificial lift methods in most cases to pump liquids to the surface, chiefly water but also oil, so that free gas can flow through the wellbore without impediment. There is no global repository of artificial lift statistics; however, industry observers estimate that 90% to 95% of the world’s producing wells currently use artificial lift, said Bill Lane, vice president of artificial lift systems emerging technologies at Weatherford. “It is trending more toward 95% than 90%, and probably 100% of producing wells would use artificial lift at some point in their lives, except for wells shut in prematurely because of economic factors.” With the ubiquity of artificial lift, “there are so many engineering opportunities in this field,” said Shauna Noonan, wells technology supervisor at ConocoPhillips and SPE technical director for production and operations. Those who embrace those opportunities will face abundant challenges, many of them related to the integration of artificial lift into unconventional horizontal wellbore designs and frontier subsea projects in deep water. Horizontal Well Challenges “Today, our technologies to sweep liquids through the lateral sections of horizontal wells are very limited,” Lane said. “To understand the challenge, note that a 5,000-ft lateral with a cased 4-in. inside diameter has the same slenderness ratio as a ¼-in. drinking straw as long as a football field. Along that straw are numerous undulations, each of which results in a sump in which liquids collect. Wherever this phenomenon occurs, the pressure beyond each sump must increase until the collected liquids are blown further toward the heel of the producing zone. This phenomenon is particularly evident in gassy liquid wells, less so in primary liquid producers.” In a perfect world for artificial lift, “the obvious solution would be toe-up straight lateral sections free from undulations,” Lane said. “But that is easier said than done.” Making wellbores straighter would help from a pumping standpoint. However, other factors usually take precedence. Bores must target the reservoir’s “sweet spots” with the most total organic content. Petrology and geophysics determine where stimulation can be most effective. Well pad designs and lease boundaries can also constrain well placement and design. Mechanical pumps have been deployed into lateral wellbore sections with limited success, experiencing higher than normal failure rates when operating on their sides and encountering problems in keeping gas separate from liquids—a necessity for efficient pump operation. Pumps with single intakes can only pull liquids from one low spot. Thus, locating a pump along a lateral bore with multiple sumps becomes a matter of compromise. For the most part, mechanical pumps are landed in the vertical or near vertical sections of horizontal wells, and are typically not landed beyond 60° deviation.

Application of biotic and abiotic indicators for detecting benthic impacts of marine salmonid farming among coastal regions of Tasmania

Analysis of sediment and macrofaunal samples collected during the Tasmanian marine farming finfish monitoring program – a six-year partnership between industry, management and researchers – revealed several univariate indicators to be useful for detecting effects of aquaculture on the benthic environment. Comparisons with reference sites revealed a significant decline in sediment redox potential to at least 4 cm depth at farm sites, and increased proportional abundance of capitellids and decreased bivalve/total mollusc ratio. At compliance sites located 35 m out from lease boundaries, sediment redox potential and faunal assemblage composition were intermediate between patterns found at farm and reference sites. Redox potential at the sediment surface declined on average by 178 eV at reference sites converted to farm sites, with this indicator proving the most sensitive for detecting regional impacts of farming activity. Fish farm effects that extended to regional scales could not be adequately assessed within the project because reference regions without fish farms were not monitored; however, a significant decrease through time at reference and compliance sites in surface redox potential, and increases in sediment organic matter and total macrofaunal abundance, were suggestive that organic enrichment may have extended at low levels across regional scales. Given the implications to biodiversity conservation of region-wide impacts and a need to distinguish fish farm effects from unrelated long-term environmental change, monitoring of reference sites in regions lacking fish farms is urgently needed.

Benthic organic enrichment from suspended mussel ( Mytilus edulis) culture in Prince Edward Island, Canada

The effects of increased biodeposition within mussel ( Mytilus edulis) farms on the benthic environment were investigated using surface sediment samples collected from 11 coastal embayments in Prince Edward Island (PEI), Canada. The degree of organic enrichment, determined using geochemical indicators (total free sulfides (S), redox potentials (Eh NHE), water content (WC) and organic matter (OM)), was significantly greater in mussel leases compared to reference sites located both outside lease boundaries and in inlets not used to culture mussel (MANOVA, p < 0.001). Post-hoc tests showed that mean WC and OM, Eh NHE potentials and S concentration were all significantly different between lease and reference sites ( p ≤ 0.009). Temporal changes in organic enrichment conditions were detected by comparing our 2001 data to those previously reported from a 1997 survey of the same sampling sites (MANOVA, p < 0.001). This multivariate effect resulted primarily from a 39% increase in mean S concentration between 1997 and 2001 ( p = 0.029). Surface sediment variables at reference sites were similar between years. Benthic conditions were discriminated along an oxic–anoxic enrichment gradient using multidimensional scaling analysis. Mussel lease sites sampled in 1997 were clustered within predefined oxic sediment classifications along with the majority of reference sites, but were grouped farther along the enrichment gradient in 2001. The significant increase in hypoxic and sulfidic sediments within mussel farms between 1997 and 2001 is consistent with the 43% increase in PEI mussel production—a classic response to excessive organic biodeposition in shallow coastal inlets with relatively low dispersive capacity.