Treatment evaluation leads to problem identification and to continuously improved treatments. The prime source of information on which to build an evaluation are the acid treatment report and the pressure and rate data during injection and falloff. Proper execution, quality control, and record keeping are prerequisites to the task of accurate evaluation. Evaluation of unsatisfactory treatments is essential to recommending changes in chemicals and/or treating techniques and procedures that will provide the best treatment for acidizing wells in the future. The most important measure of the treatment is the productivity of the well after treatment.

Equipment failures and unplanned shutdowns cost the oil and gas industry billions of dollars each year. When it comes to mitigating this risk, proper management of loss of containment is crucial within a facility from an organizational, engineering, and economic point of view. Imagine being an inspection engineer who receives 50 work orders a day with a limited time, labor, budget, and tools. How should he or she prioritize and organize the workload? Two-thirds of these costs are associated with failures of static equipment. The reason for these failures is twofold: First, the use of outdated time-based inspection for assets.

Because of current oil and gas industry economics, evaluating the return on investment for any well-intervention campaign is crucial, as is applying an assurance process to help quantify desired production improvement. This paper presents the planning and execution of a matrix-stimulation pilot project in the heavy-oil Chichimene Field in Colombia. The approach is based primarily on a work flow that includes characterizing formation damage, reviewing laboratory tests, validating well selection, and determining economically viable placement and diversion techniques. Heavy-oil reservoirs are prone to almost every formation-damage mechanism known. Damage mechanisms encountered include fines migration, paraffin and asphaltene deposition, various forms of scale, and clay swelling.

In underbalanced drilling (UBD), the hydrostatic head of the drilling fluid is intentionally designed to be lower than the pressure of the formations that are being drilled. Whether the underbalanced status is induced or natural, the result may be an influx of formation fluids that must be circulated from the well, and controlled at surface. The effective downhole circulating pressure of the drilling fluid is equal to the hydrostatic pressure of the fluid column, plus associated friction pressures, plus any pressure applied on surface. Conventionally, wells are drilled overbalanced. In these wells, a column of fluid of a certain density in the hole provides the primary well-control mechanism.

Two producer wells in the Chichimene field of Colombia were converted to injector wells as part of a water management and pressure control strategy. Because of zero injectivity in these wells, the operator desired to stimulate for a successful disposal-type reinjection to decrease the 70,000 bbl of water being discharged. This paper describes the planning and performance of stimulation operations in these two injector wells. A proper diagnostic helped to identify damage to be attributed to fines migration. Based on a consideration of petrophysical properties and corresponding logs, an acid system was designed and tested in the laboratory. Diversion options during stages of sequenced acid preflush, hydrofluoric acid, and postflush were reviewed. The desire to minimize the tubular exposure to acid in the wellbore and to place the open end of the tubing in front of the perforations made the option of coiled tubing appealing. With this option, the placement of the necessary sequential stages of the sandstone acid treatment would be possible across discrete intervals.

Both wells experienced an injectivity index of zero before the acid treatment. The average daily injection of well CH-182 dramatically increased to 19,000 BWPD after the acid treatment. The average daily injection of well CH-183 dramatically increased to 20,000 BWPD after the acid treatment.

These two wells currently have higher injection capacities than any other wells in the Chichimene field; combined, they inject 43,000 BWPD at maximum peak. The discharged water volume before the stimulation treatments was 70,000 bbl. After stimulation of the injector wells, the discharged volume is 30,000 bbl, representing an approximately 60% reduction in discharged volume.

Although Microbiologically Influenced Corrosion (MIC) is a critical damage mechanism that had been researched for decades in different environments, yet diagnosing a specific industrial failure to be attributed to MIC can still be challenging. The challenge of accurately identifying an MIC failure is partially due to the similarity of the failure morphology with other damage mechanisms, e.g., pitting corrosion due to chloride. Furthermore, the variously proposed initiation and propagation mechanisms for different types of bacteria may illustrate to the failure analyst that the MIC mechanisms are not yet well established. The confusion of MIC failure identification could also be aggravated by the fact that the presence of bacteria in a system does not necessarily mean that MIC is the culprit. Therefore, this paper will shed some light on the overlapping areas between MIC and pitting corrosion, especially the morphology of the attack. Moreover, several steps will be highlighted and discussed on how to correctly identify if MIC is the culprit in a specific failure.

The majority of inspection programs for process equipment includes conventional inspections or risk-based inspections; that consider equipment history, inspection records and various checklists etc. On the other hand, there are still numerous failures due to un-anticipated and aggravated damage mechanisms even in the presence of established inspection programs. This article highlights two different case studies where the presence of certain neighborhood conditions (even for short span of time) such as dripping water, dirt scales due to wind, and sandstorms triggered certain damage mechanisms (corrosion under insulation, short term overheating). Neighborhood conditions may also aggravate existing damage mechanisms leading to earlier and un-anticipated failure of equipment. Documentation of potential bad actors from neighborhood conditions as a part of inspection programs can minimize the uncertainties about the presence as well as severity of damage mechanisms. Such documentation will in turn aid the investigation and pro-active mitigative actions even before the occurrence of irreversible failure modes. Finally, this article provides an example of potential measures for minimizing the impact of neighborhood conditions on the occurrence and severity of CUI and short-term overheating.

Summary Dongping Field with low porosity and permeability, located in the Qaidam Basin, is the largest bedrock reservoir in China. Because of its high content of clay minerals and poor physical properties, the reservoir tends to suffer from formation damage caused by water or alkali sensitivity, which significantly affects production. Therefore, it is crucial to understand the formation‐damage mechanisms for reservoir protection and efficient development. In this paper, we propose a new method that integrates pressure‐transmission tests (PTTs) with a fixed‐point scanning electron microscope (SEM) and nuclear magnetic resonance (NMR) to investigate mechanisms of formation damage. From the macroscopic perspective, PTT, a time‐saving and accurate method of measuring permeability for tight rocks, is applied to evaluate the permeability‐damage degree of core samples. From the microscopic perspective, the change of pore structure for a specific region and the variation of the fluid volume in the core sample before and after damage are obtained by fixed‐point SEM and NMR experiments, respectively. In water‐sensitivity damage experiments, the results of PTT show that the permeability‐damage rate is approximately 60%, demonstrating that the damage degree of water sensitivity is moderate to severe. The results of the fixed‐point SEM demonstrate that the pore sizes suffer from obvious reduction as a result of water‐sensitivity damage. NMR experiments demonstrate that the main damage mechanisms vary, depending on the pore sizes. Small pores [0.1 milliseconds ≤ transverse relaxation time (T2) < 10 milliseconds] are damaged by swelling of mixed‐layer illite/smectite, and the large pores (10 milliseconds ≤ T2 <100 milliseconds) suffer from the combined damage of swelling of smectite and migration of illite. Using a similar method, the alkali‐sensitivity damage test demonstrates that there is no alkali‐sensitivity damage in target reservoirs. This novel integrated method is an efficient means to investigate the formation‐damage mechanisms for the Dongping bedrock reservoir from comprehensive perspectives. In addition, this method can be widely applied to evaluate formation damage for tight low‐permeability reservoirs.

The protection and utilization of water resources is an important theme of green mining in coal mines. Traditional longwall mining has caused problems such as loss of water resources in mining areas and death of surface vegetation. Especially in the arid and semi-arid ecologically fragile areas, simultaneously rich in coal resources in western China, the negative environmental effects of mining are particularly prominent. Coal mine groundwater reservoir can increase the total amount of water resources available and is an effective technical approach for coordinated exploitation of water and coal resources. Based on the background of shallow underground reservoir in Shendong mining area, this paper uses UDEC software to construct the numerical simulation model of dynamic damage of coal pillar dams under complex stress fields, and reveals the damage evolution law of coal pillar dams under multiple mining actions, and also uncovers the degradation response mechanism of coal pillar dams under dynamic load such as mine earthquake. By extracting the UDEC numerical simulation block unit and contact information, a numerical simulation of water content of coal pillar dams and a water immersion weakening treatment method were proposed. The “seepage-stress” coupling model of coal pillar dams is constructed, thence the development characteristics of surrounding rock fissures in mining space and the coupling development of fracture field and seepage field in coal pillar dams were studied. The results show that the damage degree of the weakened coal pillar dams was intensified, and more interpenetrating cracks were developed, which causes the seepage field to expand deep into the coal pillars, resulting in the accumulation damage effect of “water immersion weakening - coal pillar failure - seepage development - damage aggravation”. The research results provide a scientific basis for the rational design of the coal pillar dams and long-term safe operation of the underground reservoirs.