Development of low-permeability reservoirs (less than 1 mD) is carried out with intensive flooding. Injection is performed at pressure above the formation fracturing pressure that is why in almost every well a spontaneous growth of (injection) induced fractures takes place.The main problem of pressure transient analysis in a low permeability reservoir with spontaneous fracturing is a long linear regime flow observed in the log-log plot and the absence of a basis to achieve a pseudo-radial flow. To increase the accuracy of well testing in spontaneously fractured injection wells, certain field tests were developed and run. While testing, an injection well with spontaneously induced fractures was shut-in before the bottom-hole pressure went below the fracture closing pressure, then injection resumed for a short period of time, and then the well was shut-in again to record the pressure fall-off curve. The second pressure fall-off curve shows that the pseudo-radial flow developed, because the close of the part of the fracture without proppant occurred.The paper shows field examples of interference well tests exhibiting fracture growth up to 1700 m diagnosed in injection wells. Examples of successful restriction of injection well operation and application of correlation relationships of fracture closing pressure vs. formation pressure to lower water-cut in production wells with water breakthroughs are described.
Field A considered in this paper is an oil field characterized by low permeability and large vertical variability of formation properties. Injection and production take place in commingled multi-layer zones of Field A. Wells are hydraulically fractured across the entire stack of the producing layers. In the injection wells, the bottomhole pressure is higher than the formation fracturing pressures causing continuing growth of fracture length. This paper discusses 60 multi-rate injection tests to determine the injection profiles in Field A. The tests consisted of continuous measurements of the bottomhole pressures for several constant injection rates. Measurements were made for three different injection periods with pressures below and above the formation fracturing pressure. Each injection period lasted until steady-state conditions were established. Layer injection rates were determined from stabilized injection profiles obtained by spinner surveys before the tests. Layer properties were determined by matching the constant injecting rates and layer pressures for multiple injection periods. Test results demonstrated that well performances in Field A could not be described by known solutions for a constant fracture length. The non-linear relationship between the steady-state pressure and injection rate indicated that continuous change in fracture geometry had to be taken into account. These tests were useful to determine individual layer injectivities, current formation pressures and fracture opening pressures of each layer. Based on the results, it is concluded that multi-layer, multi-rate injection tests are useful to monitor layer pressure distributions and effectively produce multi-layer fields. The Simultaneous Separate Injection (SSI) technology used in these tests provides the ability to control layer injection rates and maintain uniform production from multiple layers. The SSI technology also allows injecting controlled volumes simultaneously into several layers through one injection well. Comparison of the tests using the SSI technology and adjusted valves demonstrates redistribution of injection rates from a higher- permeability layer to a lower-permeability layer.
TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractMultipay fields are often considered to be developed with a single well pattern, which is justified by economical efficiency reasons. Using smart well technologies is now on the highest peak of popularity. Although, such technologies allow intelligent monitoring and control to be performed, the most effective well regimes consideration is a challenging problem by itself. Because of system restrictions (casing diameter, wellhead pressure, infrastructure capabilities), regulating flow from/to one of the branches of such well can reflect on the overall system performance. Considering this, wells regimes should be worked out to give maximum economic efficiency. After the plan is worked out, control could be performed by choking layers with undesirable water/gas production (i.e controlling BHP). Rosneft oil company operates Priobskoye field which has three productive layers (AC10, AC11, AC12) being developed. These layers are characterized with low permeability (1 to 20 mD) and different relative permeability characteristics which leads to non-uniform waterflooding and hence, difference in production watercut by layers. In order to perform monitoring and control procedures separately with each layer, it was considered to equip injection wells with special tools. A strategy of control for such wells is described in this paper. It is based on integrated study which includes NODAL analysis, watercut prediction and well tests. For injectivity curve (P,Q) characteristics (which is non-linear due to fractures development at high BHP), multi-rate tests are being performed. These tests allow obtaining non-linear injectivity characteristics to use it in NODAL analysis tool. Besides the method and case study, general recommendations are also given.
Гидродинамические исследования скважин в многопластовых нагнетательных скважинах в условиях превышения давления закачки над давлением раскрытия трещин Альфред Давлетбаев, OOO «РН-УфаНИПИнефть», Виталий Байков, OOO «РН-УфаНИПИнефть», Эрдал Озкан, SPE, Colorado School of Mines, Тимур Гарипов, OOO «РН-УфаНИПИнефть», Тимур Усманов, OOO «РН-УфаНИПИнефть», Руслан Асмандияров, ООО «РН-Юганскнефтегаз», Андрей Слабецкий, ООО «РН-Юганскнефтегаз», Эдуард Назаргалин, ООО «РН-Юганскнефтегаз» Авторское право 2010 г., Общество инженеров-нефтяников Этот доклад был приготавливан предьявления в 2010 Российской нефтьегазовой технической конференции и выставке состоится в Москве 26-28 октабря 2010.Данный доклад был выбран для проведения презентации Программным комитетом SPE по результатам экспертизы информации, содержащейся в представленном авторами резюме. Экспертиза содержания доклада Обществом инженеров-нефтяников не выполнялась, и доклад подлежит внесению исправлений и корректировок авторами. Материал в том виде, в котором он представлен, не обязательно отражает точку зрения Общества инженеров-нефтяников, его должностных лиц или участников. Доклады, представленные на конференциях SPE, подлежат экспертизе со стороны Редакционных Комитетов Общества инженеров-нефтяников. Электронное копирование, распространение или хранение любой части данного доклада в коммерческих целях без предварительного письменного согласия Общества инженеров-нефтяников запрещается. Разрешение на воспроизведение в печатном виде распространяется только на резюме длиной не более 300 слов; при этом копировать иллюстрации не разрешается. Резюме должно содержать явно выраженную ссылку на то, где и кем был представлен данный доклад. Write Librarian, SPE, P.O.Box 833836, Richardson, TX 75083-3836 U.S.A., факс 01-972-952-9435. РезюмеПласты месторождения А характеризуются низкой проводимостью и высокой расчлененностью пластов. Ведется совместная эксплуатация нескольких пластов единой сеткой скважин, на всех пластах проводится гидроразрыв пласта (ГРП). Давление закачки в нагнетательных скважинах выше давления раскрытия трещины зафиксированного при операции ГРП, имеет место самопроизвольное развитие техногенных трещин.В данной работе приведены результаты исследования многопластовых нагнетательных скважин на установившихся режимах закачки с замерами профиля приемистости по стволу (проведено более 60 исследований). Исследование проводится на нескольких режимах с различным давлением нагнетания. Как правило, регистрируется по 3 режима при давлении закачки ниже и выше давления раскрытия трещины. На установившихся режимах закачки проводится комплекс промыслово-геофизических исследований с регистрацией профиля приемистости по пластам в многопластовой скважине. Полученные данные расхода и давления закачки по каждому пласту обрабатываются методом построения индикаторной диаграммы.Проведенные эксперименты показали, что при забойном давлении выше давления раскрытия трещин течение в системе «скважина-трещина-пласт» не описывается известным решением о притоке в трещину ГРП с фиксиро...
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